TP
Tobias Pluess
Tue, Apr 14, 2020 6:23 AM
Hey Bob
ok now I see your point! you talk about the phase spillovers. Timelab and
also Stable32 can correct for them, so it shouldn't be a problem, right?
But I agree, if you cannot correct for the spillovers it becomes even more
difficult.
Tobias
On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, kb8tq@n1k.org wrote:
Hi
The gotcha with using a conventional counter (as opposed to a time tagger)
is that you never know when things are going to “slip” past each other.
When they
do you get a major burp in your data. Bill’s setup is running a time
tagger ….
( = It runs an internal time count, each edge gets “labeled” with a
precise time
stamp that is good to nanoseconds or picoseconds. A Time Interval Counter
simply measures the time between edges. That sounds like the same thing,
but
it’s not quite ….)
to compare two oscillators.
I don't know exactly how, though :-)
The gotcha with using a conventional counter (as opposed to a time tagger)
is that you never know when things are going to “slip” past each other.
When they
do you get a major burp in your data. Bill’s setup is running a time
tagger ….
OK and I see your point on the 8663. I will try to use another reference!
I definitely didn't keep mine on for a long time. I didn't use the signal
generator for a while now, so it was unplugged for a few months. I assume
that's far from optimal for the 10811's stability.
Best approach is to mount your reference off on it’s own and just power
it. That way
you don’t wear out all the guts of a fancy piece of gear.
Bob
Tobias
On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, kb8tq@n1k.org wrote:
On Apr 13, 2020, at 5:06 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi Bob
awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
Maybe I have some good OpAmps for this purpose in my box. I will try
of
You need something that is quiet (like the OP-37) and has a pretty good
slew
rate. Past that, there are a lot of candidates. The TI OPA-228 family is
one.
course I saw that my setup was not ideal as there was a bit of noise on
signals which I guess does lead to some jitter in the trigger circuit
therefore decreases my measurement noise floor.
Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
digits.
Net result is a measurement that’s good in the vicinity of parts in
Can you say something about how it would be done using a TIC?
I don't have two identically good counters, but the HP 5335A could be
The standard way of doing the test is to run two counters / two TIC/s /
two whatever’s.
I know of no practical way to do it with a single 5335.
And the offset source I used is not directly the HP 10811, but the HP
Signal generator internally uses a 10811 as reference source. But I
wait for days for it to warm up properly. (Should I?)
The 8663 synthesizer adds a lot of crud to the 10811. Regardless of
you
use the 10811, it needs to be on for a while. How long very much depends
on
just how long it’s been off. Best to keep it on all the time.
Yea, of course! :-)
I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
myself. I use TimeLab to see what numbers I should expect, and then I
to compute it all myself in Matlab because I want to see how it
Be careful any time you code this stuff for the first time. It’s
easy
( = I’ve done it ….) to make minor errors. That’s in no way to suggest
you should not code it up yourself. I generally do it in Excel or in C.
Bob
Best
Tobias
On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
Ok, first the math:
If your offset oscillator is 10 Hz high at 10 MHz, you have a:
10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
You get to add a 6 to what Time Lab shows you.
If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
gets you to 1x10^-10
So, what’s going on?
You can’t feed the mixer outputs straight into a counter. The counter
front
end does not handle LF audio sine waves very well. You need to do an
op-amp based limiter. A pair of OP-37’s in each leg ( or something
similar)
should do the trick.
Second, the offset source needs to be pretty good. A 10811 tuned high
both the mechanical trim and the EFC is a pretty good choice to start
If you only have one counter, simply ignore the second channel. You
running a single mixer. It still works as a comparison between the
oscillator
and your DUT.
If you want to do it properly as a DMTD, then you set up two counters.
to measure mixer A and the other to measure mixer B. Set them both up
measure frequency. Time tag the data files so you know which reading
matches up with which.
Fun !!!
Bob
On Apr 13, 2020, at 3:18 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi again Bob
I tried to do some measurements with a DMTD!
In my junk box I found a little PCB from earlier experiments on that
with a power splitter and two SRA-3H mixers, it was even already
the DMTD configuration. So I gave it a try!
As "transfer oscillator" I used my HP 8663A signal generator, and set
high in frequency by 10 Hz. To the two mixers, I connected the two
signals and at the mixer outputs, I put a little lowpass filter with
corner frequency.
The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
to feed them directly into the HP 5335A TIC and used the TI mode to
the delay between the two signals.
This gives 10 readings/sec, which I try to process with TimeLab.
It does give some interesting graphs, but I don't know yet how to
set up TimeLab for this kind of measurement. I.e. now, I get an ADEV
order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
simply need to multiply this with 1e-7 to get the real ADEV at
this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
is indeed my target value, BUT I expect that things are not that
(i.e. what if I didn't set the transfer oscillator high by +10Hz but
by 9.9Hz for example).
Can you give some hints on that?
Of course I also did the noise floor test (i.e. I fed the 10MHz
a power splitter and connected the two outputs to my DMTD with two
different lenghts of cables. This gave results starting at 1e-4 going
to 1e-7, maybe it would have gone even lower but I measured only for
couple of minutes.)
Can you give some hints on that?
Best
Tobias
HB9FSX
On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
The quick way to do this is with a single mixer. Take something
old
10811 and use the coarse tune to set it high in frequency by 5 to
Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
That tone is the difference between the 10811 and your device
test.
If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
If you measured the 10 MHz on the DUT, that 1 Hz would be a very
shift
( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
IF you could tack that on to the ADEV plot of your 5335 ( no,
that
simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
second.
The reason its not quite that simple is that the input circuit on
counter
really does not handle a 10 Hz audio tone as well as it handles a
RF signal. Instead of getting 9 digits a second, you probably will
three
good digits a second and another 6 digits of noise.
The good news is that an op amp used as a preamp ( to get you up to
32 V p-p rather than a volt or so) and another op amp or three as
limiters will
get you up around 6 or 7 good digits. Toss in a cap or two as a
and low pass filter ( DC offsets can be a problem ….) and you have
working
device that gets into the parts in 10^-13 with your 5335.
It all can be done with point to point wiring. No need for a PCB
Be
careful that the +/- 18V supplies to the op amp both go on and
and follow the instructions there.
and follow the instructions there.
and follow the instructions there.
Hey Bob
ok now I see your point! you talk about the phase spillovers. Timelab and
also Stable32 can correct for them, so it shouldn't be a problem, right?
But I agree, if you cannot correct for the spillovers it becomes even more
difficult.
Tobias
On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, <kb8tq@n1k.org> wrote:
> Hi
>
> The gotcha with using a conventional counter (as opposed to a time tagger)
> is that you never know when things are going to “slip” past each other.
> When they
> do you get a major burp in your data. Bill’s setup is running a time
> tagger ….
>
> ( = It runs an internal time count, each edge gets “labeled” with a
> precise time
> stamp that is good to nanoseconds or picoseconds. A Time Interval Counter
> simply measures the time between edges. That sounds like the same thing,
> but
> it’s not quite ….)
>
>
> > On Apr 13, 2020, at 6:11 PM, Tobias Pluess <tpluess@ieee.org> wrote:
> >
> > Hi Bob
> >
> > Riley suggests to use a single TIC
> >
> > http://wriley.com/A%20Small%20DMTD%20System.pdf
> >
> > when you look at the block diagram Fig. 4, you can see that one TIC
> allows
> > to compare two oscillators.
> > I don't know exactly how, though :-)
>
> The gotcha with using a conventional counter (as opposed to a time tagger)
> is that you never know when things are going to “slip” past each other.
> When they
> do you get a major burp in your data. Bill’s setup is running a time
> tagger ….
>
> >
> > OK and I see your point on the 8663. I will try to use another reference!
> > I definitely didn't keep mine on for a long time. I didn't use the signal
> > generator for a while now, so it was unplugged for a few months. I assume
> > that's far from optimal for the 10811's stability.
>
> Best approach is to mount your reference off on it’s own and just power
> it. That way
> you don’t wear out all the guts of a fancy piece of gear.
>
> Bob
>
> >
> >
> > Tobias
> >
> >
> >
> > On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote:
> >
> >> Hi
> >>
> >>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote:
> >>>
> >>> Hi Bob
> >>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
> >>>
> >>> Maybe I have some good OpAmps for this purpose in my box. I will try
> it!
> >> of
> >>
> >> You need something that is quiet (like the OP-37) and has a pretty good
> >> slew
> >> rate. Past that, there are a lot of candidates. The TI OPA-228 family is
> >> one.
> >>
> >>> course I saw that my setup was not ideal as there was a bit of noise on
> >> the
> >>> signals which I guess does lead to some jitter in the trigger circuit
> and
> >>> therefore decreases my measurement noise floor.
> >>
> >> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
> >> digits.
> >> Net result is a measurement that’s good in the vicinity of parts in
> 10^-13
> >>
> >>>
> >>> Can you say something about how it would be done using a TIC?
> >>> I don't have two identically good counters, but the HP 5335A could be
> >> used
> >>> as TIC, couldn't it.
> >>
> >> The standard way of doing the test is to run two counters / two TIC/s /
> >> two whatever’s.
> >> I know of no practical way to do it with a single 5335.
> >>
> >>>
> >>> And the offset source I used is not directly the HP 10811, but the HP
> >> 8663A
> >>> Signal generator internally uses a 10811 as reference source. But I
> >> didn't
> >>> wait for days for it to warm up properly. (Should I?)
> >>
> >> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of
> how
> >> you
> >> use the 10811, it needs to be on for a while. How long very much depends
> >> on
> >> just how long it’s been off. Best to keep it on all the time.
> >>
> >>>
> >>>> Fun !!!
> >>> Yea, of course! :-)
> >>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
> >>> myself. I use TimeLab to see what numbers I should expect, and then I
> >> want
> >>> to compute it all myself in Matlab because I want to see how it
> actually
> >>> works. ;-)
> >>
> >> Be careful any time you code this stuff for the first time. It’s
> amazingly
> >> easy
> >> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest
> that
> >> you should not code it up yourself. I generally do it in Excel or in C.
> >>
> >> Bob
> >>
> >>>
> >>>
> >>> Best
> >>> Tobias
> >>>
> >>>
> >>>
> >>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >>>
> >>>> Hi
> >>>>
> >>>> Ok, first the math:
> >>>>
> >>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
> >>>>
> >>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
> >>>>
> >>>> You get to add a 6 to what Time Lab shows you.
> >>>>
> >>>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
> >>>> gets you to 1x10^-10
> >>>>
> >>>> So, what’s going on?
> >>>>
> >>>> You can’t feed the mixer outputs straight into a counter. The counter
> >>>> front
> >>>> end does not handle LF audio sine waves very well. You need to do an
> >>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
> >>>> similar)
> >>>> should do the trick.
> >>>>
> >>>> Second, the offset source needs to be pretty good. A 10811 tuned high
> >> with
> >>>> both the mechanical trim and the EFC is a pretty good choice to start
> >> out.
> >>>>
> >>>> If you only have one counter, simply ignore the second channel. You
> are
> >> now
> >>>> running a single mixer. It still works as a comparison between the
> >> offset
> >>>> oscillator
> >>>> and your DUT.
> >>>>
> >>>> If you want to do it properly as a DMTD, then you set up two counters.
> >> One
> >>>> to measure mixer A and the other to measure mixer B. Set them both up
> >> to
> >>>> measure frequency. Time tag the data files so you know which reading
> >>>> matches up with which.
> >>>>
> >>>> Fun !!!
> >>>>
> >>>> Bob
> >>>>
> >>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote:
> >>>>>
> >>>>> Hi again Bob
> >>>>>
> >>>>> I tried to do some measurements with a DMTD!
> >>>>> In my junk box I found a little PCB from earlier experiments on that
> >>>> topic,
> >>>>> with a power splitter and two SRA-3H mixers, it was even already
> wired
> >>>> for
> >>>>> the DMTD configuration. So I gave it a try!
> >>>>> As "transfer oscillator" I used my HP 8663A signal generator, and set
> >> it
> >>>>> high in frequency by 10 Hz. To the two mixers, I connected the two
> >> 10MHz
> >>>>> signals and at the mixer outputs, I put a little lowpass filter with
> >>>> 100Hz
> >>>>> corner frequency.
> >>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
> >>>> tried
> >>>>> to feed them directly into the HP 5335A TIC and used the TI mode to
> >>>> measure
> >>>>> the delay between the two signals.
> >>>>> This gives 10 readings/sec, which I try to process with TimeLab.
> >>>>> It does give some interesting graphs, but I don't know yet how to
> >>>> correctly
> >>>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV
> in
> >>>> the
> >>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
> mean
> >> I
> >>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at
> 10MHz?
> >>>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
> >>>> which
> >>>>> is indeed my target value, BUT I expect that things are not that
> >> simple.
> >>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but
> >> only
> >>>>> by 9.9Hz for example).
> >>>>> Can you give some hints on that?
> >>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz
> signal
> >>>> into
> >>>>> a power splitter and connected the two outputs to my DMTD with two
> >>>>> different lenghts of cables. This gave results starting at 1e-4 going
> >>>> down
> >>>>> to 1e-7, maybe it would have gone even lower but I measured only for
> a
> >>>>> couple of minutes.)
> >>>>>
> >>>>> Can you give some hints on that?
> >>>>>
> >>>>> Best
> >>>>> Tobias
> >>>>> HB9FSX
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >>>>>>
> >>>>>>> Hi
> >>>>>>>
> >>>>>>> The quick way to do this is with a single mixer. Take something
> like
> >> an
> >>>>>>> old
> >>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to
> 10
> >>>> Hz.
> >>>>>>>
> >>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
> >>>> tone.
> >>>>>>> That tone is the *difference* between the 10811 and your device
> under
> >>>>>>> test.
> >>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
> >>>>>>>
> >>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very
> >> small
> >>>>>>> shift
> >>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
> >>>> change
> >>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
> >> increase
> >>>> ).
> >>>>>>>
> >>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no,
> it’s
> >>>> not
> >>>>>>> that
> >>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
> >>>>>>> second.
> >>>>>>>
> >>>>>>> The reason its not quite that simple is that the input circuit on
> the
> >>>>>>> counter
> >>>>>>> really does not handle a 10 Hz audio tone as well as it handles a
> 10
> >>>> MHz
> >>>>>>> RF signal. Instead of getting 9 digits a second, you probably will
> >> get
> >>>>>>> three
> >>>>>>> *good* digits a second and another 6 digits of noise.
> >>>>>>>
> >>>>>>> The good news is that an op amp used as a preamp ( to get you up to
> >>>> maybe
> >>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as
> >>>>>>> limiters will
> >>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a
> high
> >>>> pass
> >>>>>>> and low pass filter ( DC offsets can be a problem ….) and you have
> a
> >>>>>>> working
> >>>>>>> device that gets into the parts in 10^-13 with your 5335.
> >>>>>>>
> >>>>>>> It all can be done with point to point wiring. No need for a PCB
> >>>> layout.
> >>>>>>> Be
> >>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and
> off
> >> at
> >>>>>>> the
> >>>>>>> same time ….
> >>>>>>>
> >>>>>>> Bob
> >>>>>>>
> >>>>>>
> >>>>> _______________________________________________
> >>>>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>>>> To unsubscribe, go to
> >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>>>> and follow the instructions there.
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>>> To unsubscribe, go to
> >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>>> and follow the instructions there.
> >>>>
> >>> _______________________________________________
> >>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>> and follow the instructions there.
> >>
> >>
> >> _______________________________________________
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >>
> > _______________________________________________
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
TP
Tobias Pluess
Tue, Apr 14, 2020 6:31 AM
Hi Taka
good to know you're working on the same stuff :-)
I also think that this is the goal, sort of. But apparently there are some
pitfalls. I hope the experts on this type of measurement (Bob) can give
more hints ;-)
Btw good to know your 10811 took 2 months to settle. In that case I will
try to give mine also more time from power up until I do measurements. But
keeping the 8663 powered on is almost no option for me - my homelab is
simply too small and from time to time I therefore have to tidy it up a bit
and put some of the equipment in another shelf.
Tobias
On Tue., 14 Apr. 2020, 01:19 Taka Kamiya via time-nuts, <
time-nuts@lists.febo.com> wrote:
I am working on pretty much the same thing. My HP105B has an HP11801
inside. There is no telling how long it has been off. Frequency wandered
ALL OVER THE PLACE. It took 2 months of continuous operation to settle
down and just do the normal aging/drifting.
I have a same question as you do. How come not just one HP5335? Your
test setup has two output. One goes to start, the other goes to stop.
Measure the time interval. Isn't that the goal?
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Monday, April 13, 2020, 5:53:52 PM EDT, Bob kb8tq <kb8tq@n1k.org>
wrote:
Hi
On Apr 13, 2020, at 5:06 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi Bob
awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
Maybe I have some good OpAmps for this purpose in my box. I will try it!
of
You need something that is quiet (like the OP-37) and has a pretty good
slew
rate. Past that, there are a lot of candidates. The TI OPA-228 family is
one.
course I saw that my setup was not ideal as there was a bit of noise on
signals which I guess does lead to some jitter in the trigger circuit and
therefore decreases my measurement noise floor.
Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
digits.
Net result is a measurement that’s good in the vicinity of parts in 10^-13
Can you say something about how it would be done using a TIC?
I don't have two identically good counters, but the HP 5335A could be
The standard way of doing the test is to run two counters / two TIC/s /
two whatever’s.
I know of no practical way to do it with a single 5335.
And the offset source I used is not directly the HP 10811, but the HP
Signal generator internally uses a 10811 as reference source. But I
wait for days for it to warm up properly. (Should I?)
The 8663 synthesizer adds a lot of crud to the 10811. Regardless of how
you
use the 10811, it needs to be on for a while. How long very much depends
on
just how long it’s been off. Best to keep it on all the time.
Yea, of course! :-)
I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
myself. I use TimeLab to see what numbers I should expect, and then I
to compute it all myself in Matlab because I want to see how it actually
works. ;-)
Be careful any time you code this stuff for the first time. It’s amazingly
easy
( = I’ve done it ….) to make minor errors. That’s in no way to suggest that
you should not code it up yourself. I generally do it in Excel or in C.
Bob
Best
Tobias
On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
Ok, first the math:
If your offset oscillator is 10 Hz high at 10 MHz, you have a:
10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
You get to add a 6 to what Time Lab shows you.
If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
gets you to 1x10^-10
So, what’s going on?
You can’t feed the mixer outputs straight into a counter. The counter
front
end does not handle LF audio sine waves very well. You need to do an
op-amp based limiter. A pair of OP-37’s in each leg ( or something
similar)
should do the trick.
Second, the offset source needs to be pretty good. A 10811 tuned high
both the mechanical trim and the EFC is a pretty good choice to start
If you only have one counter, simply ignore the second channel. You are
running a single mixer. It still works as a comparison between the
oscillator
and your DUT.
If you want to do it properly as a DMTD, then you set up two counters.
to measure mixer A and the other to measure mixer B. Set them both up
measure frequency. Time tag the data files so you know which reading
matches up with which.
Fun !!!
Bob
On Apr 13, 2020, at 3:18 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi again Bob
I tried to do some measurements with a DMTD!
In my junk box I found a little PCB from earlier experiments on that
with a power splitter and two SRA-3H mixers, it was even already wired
the DMTD configuration. So I gave it a try!
As "transfer oscillator" I used my HP 8663A signal generator, and set
high in frequency by 10 Hz. To the two mixers, I connected the two
signals and at the mixer outputs, I put a little lowpass filter with
corner frequency.
The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
to feed them directly into the HP 5335A TIC and used the TI mode to
the delay between the two signals.
This gives 10 readings/sec, which I try to process with TimeLab.
It does give some interesting graphs, but I don't know yet how to
set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in
order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean
simply need to multiply this with 1e-7 to get the real ADEV at 10MHz?
this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
is indeed my target value, BUT I expect that things are not that
(i.e. what if I didn't set the transfer oscillator high by +10Hz but
by 9.9Hz for example).
Can you give some hints on that?
Of course I also did the noise floor test (i.e. I fed the 10MHz signal
a power splitter and connected the two outputs to my DMTD with two
different lenghts of cables. This gave results starting at 1e-4 going
to 1e-7, maybe it would have gone even lower but I measured only for a
couple of minutes.)
Can you give some hints on that?
Best
Tobias
HB9FSX
On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
The quick way to do this is with a single mixer. Take something like
old
10811 and use the coarse tune to set it high in frequency by 5 to 10
Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
That tone is the difference between the 10811 and your device under
test.
If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
If you measured the 10 MHz on the DUT, that 1 Hz would be a very
shift
( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
IF you could tack that on to the ADEV plot of your 5335 ( no, it’s
that
simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
second.
The reason its not quite that simple is that the input circuit on the
counter
really does not handle a 10 Hz audio tone as well as it handles a 10
RF signal. Instead of getting 9 digits a second, you probably will
three
good digits a second and another 6 digits of noise.
The good news is that an op amp used as a preamp ( to get you up to
32 V p-p rather than a volt or so) and another op amp or three as
limiters will
get you up around 6 or 7 good digits. Toss in a cap or two as a high
and low pass filter ( DC offsets can be a problem ….) and you have a
working
device that gets into the parts in 10^-13 with your 5335.
It all can be done with point to point wiring. No need for a PCB
Be
careful that the +/- 18V supplies to the op amp both go on and off
and follow the instructions there.
and follow the instructions there.
Hi Taka
good to know you're working on the same stuff :-)
I also think that this is the goal, sort of. But apparently there are some
pitfalls. I hope the experts on this type of measurement (Bob) can give
more hints ;-)
Btw good to know your 10811 took 2 months to settle. In that case I will
try to give mine also more time from power up until I do measurements. But
keeping the 8663 powered on is almost no option for me - my homelab is
simply too small and from time to time I therefore have to tidy it up a bit
and put some of the equipment in another shelf.
Tobias
On Tue., 14 Apr. 2020, 01:19 Taka Kamiya via time-nuts, <
time-nuts@lists.febo.com> wrote:
> I am working on pretty much the same thing. My HP105B has an HP11801
> inside. There is no telling how long it has been off. Frequency wandered
> ALL OVER THE PLACE. It took 2 months of continuous operation to settle
> down and just do the normal aging/drifting.
>
> I have a same question as you do. How come not just one HP5335? Your
> test setup has two output. One goes to start, the other goes to stop.
> Measure the time interval. Isn't that the goal?
>
> ---------------------------------------
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
>
>
> On Monday, April 13, 2020, 5:53:52 PM EDT, Bob kb8tq <kb8tq@n1k.org>
> wrote:
>
> Hi
>
> > On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote:
> >
> > Hi Bob
> > awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
> >
> > Maybe I have some good OpAmps for this purpose in my box. I will try it!
> of
>
> You need something that is quiet (like the OP-37) and has a pretty good
> slew
> rate. Past that, there are a lot of candidates. The TI OPA-228 family is
> one.
>
> > course I saw that my setup was not ideal as there was a bit of noise on
> the
> > signals which I guess does lead to some jitter in the trigger circuit and
> > therefore decreases my measurement noise floor.
>
> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
> digits.
> Net result is a measurement that’s good in the vicinity of parts in 10^-13
>
> >
> > Can you say something about how it would be done using a TIC?
> > I don't have two identically good counters, but the HP 5335A could be
> used
> > as TIC, couldn't it.
>
> The standard way of doing the test is to run two counters / two TIC/s /
> two whatever’s.
> I know of no practical way to do it with a single 5335.
>
> >
> > And the offset source I used is not directly the HP 10811, but the HP
> 8663A
> > Signal generator internally uses a 10811 as reference source. But I
> didn't
> > wait for days for it to warm up properly. (Should I?)
>
> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of how
> you
> use the 10811, it needs to be on for a while. How long very much depends
> on
> just how long it’s been off. Best to keep it on all the time.
>
> >
> >> Fun !!!
> > Yea, of course! :-)
> > I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
> > myself. I use TimeLab to see what numbers I should expect, and then I
> want
> > to compute it all myself in Matlab because I want to see how it actually
> > works. ;-)
>
> Be careful any time you code this stuff for the first time. It’s amazingly
> easy
> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest that
> you should not code it up yourself. I generally do it in Excel or in C.
>
> Bob
>
> >
> >
> > Best
> > Tobias
> >
> >
> >
> > On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >
> >> Hi
> >>
> >> Ok, first the math:
> >>
> >> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
> >>
> >> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
> >>
> >> You get to add a 6 to what Time Lab shows you.
> >>
> >> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
> >> gets you to 1x10^-10
> >>
> >> So, what’s going on?
> >>
> >> You can’t feed the mixer outputs straight into a counter. The counter
> >> front
> >> end does not handle LF audio sine waves very well. You need to do an
> >> op-amp based limiter. A pair of OP-37’s in each leg ( or something
> >> similar)
> >> should do the trick.
> >>
> >> Second, the offset source needs to be pretty good. A 10811 tuned high
> with
> >> both the mechanical trim and the EFC is a pretty good choice to start
> out.
> >>
> >> If you only have one counter, simply ignore the second channel. You are
> now
> >> running a single mixer. It still works as a comparison between the
> offset
> >> oscillator
> >> and your DUT.
> >>
> >> If you want to do it properly as a DMTD, then you set up two counters.
> One
> >> to measure mixer A and the other to measure mixer B. Set them both up
> to
> >> measure frequency. Time tag the data files so you know which reading
> >> matches up with which.
> >>
> >> Fun !!!
> >>
> >> Bob
> >>
> >>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote:
> >>>
> >>> Hi again Bob
> >>>
> >>> I tried to do some measurements with a DMTD!
> >>> In my junk box I found a little PCB from earlier experiments on that
> >> topic,
> >>> with a power splitter and two SRA-3H mixers, it was even already wired
> >> for
> >>> the DMTD configuration. So I gave it a try!
> >>> As "transfer oscillator" I used my HP 8663A signal generator, and set
> it
> >>> high in frequency by 10 Hz. To the two mixers, I connected the two
> 10MHz
> >>> signals and at the mixer outputs, I put a little lowpass filter with
> >> 100Hz
> >>> corner frequency.
> >>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
> >> tried
> >>> to feed them directly into the HP 5335A TIC and used the TI mode to
> >> measure
> >>> the delay between the two signals.
> >>> This gives 10 readings/sec, which I try to process with TimeLab.
> >>> It does give some interesting graphs, but I don't know yet how to
> >> correctly
> >>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in
> >> the
> >>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean
> I
> >>> simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz?
> >>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
> >> which
> >>> is indeed my target value, BUT I expect that things are not that
> simple.
> >>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but
> only
> >>> by 9.9Hz for example).
> >>> Can you give some hints on that?
> >>> Of course I also did the noise floor test (i.e. I fed the 10MHz signal
> >> into
> >>> a power splitter and connected the two outputs to my DMTD with two
> >>> different lenghts of cables. This gave results starting at 1e-4 going
> >> down
> >>> to 1e-7, maybe it would have gone even lower but I measured only for a
> >>> couple of minutes.)
> >>>
> >>> Can you give some hints on that?
> >>>
> >>> Best
> >>> Tobias
> >>> HB9FSX
> >>>
> >>>
> >>>
> >>>
> >>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >>>>
> >>>>> Hi
> >>>>>
> >>>>> The quick way to do this is with a single mixer. Take something like
> an
> >>>>> old
> >>>>> 10811 and use the coarse tune to set it high in frequency by 5 to 10
> >> Hz.
> >>>>>
> >>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
> >> tone.
> >>>>> That tone is the *difference* between the 10811 and your device under
> >>>>> test.
> >>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
> >>>>>
> >>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very
> small
> >>>>> shift
> >>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
> >> change
> >>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
> increase
> >> ).
> >>>>>
> >>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, it’s
> >> not
> >>>>> that
> >>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
> >>>>> second.
> >>>>>
> >>>>> The reason its not quite that simple is that the input circuit on the
> >>>>> counter
> >>>>> really does not handle a 10 Hz audio tone as well as it handles a 10
> >> MHz
> >>>>> RF signal. Instead of getting 9 digits a second, you probably will
> get
> >>>>> three
> >>>>> *good* digits a second and another 6 digits of noise.
> >>>>>
> >>>>> The good news is that an op amp used as a preamp ( to get you up to
> >> maybe
> >>>>> 32 V p-p rather than a volt or so) and another op amp or three as
> >>>>> limiters will
> >>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a high
> >> pass
> >>>>> and low pass filter ( DC offsets can be a problem ….) and you have a
> >>>>> working
> >>>>> device that gets into the parts in 10^-13 with your 5335.
> >>>>>
> >>>>> It all can be done with point to point wiring. No need for a PCB
> >> layout.
> >>>>> Be
> >>>>> careful that the +/- 18V supplies to the op amp *both* go on and off
> at
> >>>>> the
> >>>>> same time ….
> >>>>>
> >>>>> Bob
> >>>>>
> >>>>
> >>> _______________________________________________
> >>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>> and follow the instructions there.
> >>
> >>
> >> _______________________________________________
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >>
> > _______________________________________________
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
BK
Bob kb8tq
Tue, Apr 14, 2020 11:47 AM
Hi
If the phase slips are “well behaved” they can be handled. The problem
with a dual channel setup is that they are often not well behaved. The
period is 100 ns so a frequency drift of 1 ppb will put you in trouble in
under 2 minutes.
The only real answer is to do it properly and time tag the two outputs.
Any other approach will get you yelling and screaming at the test set.
Playing with two counters and not time tagging is in the “yelling and
screaming” category as well.
Get a TAPPR TICC if you really want to do a DMTD.
Of course you could just use a single mixer. That works fine with the
counter you already have. It will give you an A to B test just like a
DMTD. The only limitation is the need to tune at least one of the oscillators
in each pair.
There is no requirement that you tune only one. If both are tunable,
you could tune one to the high end of its range and the other to the low end.
With most OCXO’s, there is plenty of tune range.
Bob
On Apr 14, 2020, at 2:23 AM, Tobias Pluess tpluess@ieee.org wrote:
Hey Bob
ok now I see your point! you talk about the phase spillovers. Timelab and
also Stable32 can correct for them, so it shouldn't be a problem, right?
But I agree, if you cannot correct for the spillovers it becomes even more
difficult.
Tobias
On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, kb8tq@n1k.org wrote:
Hi
The gotcha with using a conventional counter (as opposed to a time tagger)
is that you never know when things are going to “slip” past each other.
When they
do you get a major burp in your data. Bill’s setup is running a time
tagger ….
( = It runs an internal time count, each edge gets “labeled” with a
precise time
stamp that is good to nanoseconds or picoseconds. A Time Interval Counter
simply measures the time between edges. That sounds like the same thing,
but
it’s not quite ….)
to compare two oscillators.
I don't know exactly how, though :-)
The gotcha with using a conventional counter (as opposed to a time tagger)
is that you never know when things are going to “slip” past each other.
When they
do you get a major burp in your data. Bill’s setup is running a time
tagger ….
OK and I see your point on the 8663. I will try to use another reference!
I definitely didn't keep mine on for a long time. I didn't use the signal
generator for a while now, so it was unplugged for a few months. I assume
that's far from optimal for the 10811's stability.
Best approach is to mount your reference off on it’s own and just power
it. That way
you don’t wear out all the guts of a fancy piece of gear.
Bob
Tobias
On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, kb8tq@n1k.org wrote:
On Apr 13, 2020, at 5:06 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi Bob
awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
Maybe I have some good OpAmps for this purpose in my box. I will try
of
You need something that is quiet (like the OP-37) and has a pretty good
slew
rate. Past that, there are a lot of candidates. The TI OPA-228 family is
one.
course I saw that my setup was not ideal as there was a bit of noise on
signals which I guess does lead to some jitter in the trigger circuit
therefore decreases my measurement noise floor.
Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
digits.
Net result is a measurement that’s good in the vicinity of parts in
Can you say something about how it would be done using a TIC?
I don't have two identically good counters, but the HP 5335A could be
The standard way of doing the test is to run two counters / two TIC/s /
two whatever’s.
I know of no practical way to do it with a single 5335.
And the offset source I used is not directly the HP 10811, but the HP
Signal generator internally uses a 10811 as reference source. But I
wait for days for it to warm up properly. (Should I?)
The 8663 synthesizer adds a lot of crud to the 10811. Regardless of
you
use the 10811, it needs to be on for a while. How long very much depends
on
just how long it’s been off. Best to keep it on all the time.
Yea, of course! :-)
I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
myself. I use TimeLab to see what numbers I should expect, and then I
to compute it all myself in Matlab because I want to see how it
Be careful any time you code this stuff for the first time. It’s
easy
( = I’ve done it ….) to make minor errors. That’s in no way to suggest
you should not code it up yourself. I generally do it in Excel or in C.
Bob
Best
Tobias
On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
Ok, first the math:
If your offset oscillator is 10 Hz high at 10 MHz, you have a:
10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
You get to add a 6 to what Time Lab shows you.
If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
gets you to 1x10^-10
So, what’s going on?
You can’t feed the mixer outputs straight into a counter. The counter
front
end does not handle LF audio sine waves very well. You need to do an
op-amp based limiter. A pair of OP-37’s in each leg ( or something
similar)
should do the trick.
Second, the offset source needs to be pretty good. A 10811 tuned high
both the mechanical trim and the EFC is a pretty good choice to start
If you only have one counter, simply ignore the second channel. You
running a single mixer. It still works as a comparison between the
oscillator
and your DUT.
If you want to do it properly as a DMTD, then you set up two counters.
to measure mixer A and the other to measure mixer B. Set them both up
measure frequency. Time tag the data files so you know which reading
matches up with which.
Fun !!!
Bob
On Apr 13, 2020, at 3:18 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi again Bob
I tried to do some measurements with a DMTD!
In my junk box I found a little PCB from earlier experiments on that
with a power splitter and two SRA-3H mixers, it was even already
the DMTD configuration. So I gave it a try!
As "transfer oscillator" I used my HP 8663A signal generator, and set
high in frequency by 10 Hz. To the two mixers, I connected the two
signals and at the mixer outputs, I put a little lowpass filter with
corner frequency.
The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
to feed them directly into the HP 5335A TIC and used the TI mode to
the delay between the two signals.
This gives 10 readings/sec, which I try to process with TimeLab.
It does give some interesting graphs, but I don't know yet how to
set up TimeLab for this kind of measurement. I.e. now, I get an ADEV
order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
simply need to multiply this with 1e-7 to get the real ADEV at
this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
is indeed my target value, BUT I expect that things are not that
(i.e. what if I didn't set the transfer oscillator high by +10Hz but
by 9.9Hz for example).
Can you give some hints on that?
Of course I also did the noise floor test (i.e. I fed the 10MHz
a power splitter and connected the two outputs to my DMTD with two
different lenghts of cables. This gave results starting at 1e-4 going
to 1e-7, maybe it would have gone even lower but I measured only for
couple of minutes.)
Can you give some hints on that?
Best
Tobias
HB9FSX
On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
The quick way to do this is with a single mixer. Take something
old
10811 and use the coarse tune to set it high in frequency by 5 to
Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
That tone is the difference between the 10811 and your device
test.
If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
If you measured the 10 MHz on the DUT, that 1 Hz would be a very
shift
( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
IF you could tack that on to the ADEV plot of your 5335 ( no,
that
simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
second.
The reason its not quite that simple is that the input circuit on
counter
really does not handle a 10 Hz audio tone as well as it handles a
RF signal. Instead of getting 9 digits a second, you probably will
three
good digits a second and another 6 digits of noise.
The good news is that an op amp used as a preamp ( to get you up to
32 V p-p rather than a volt or so) and another op amp or three as
limiters will
get you up around 6 or 7 good digits. Toss in a cap or two as a
and low pass filter ( DC offsets can be a problem ….) and you have
working
device that gets into the parts in 10^-13 with your 5335.
It all can be done with point to point wiring. No need for a PCB
Be
careful that the +/- 18V supplies to the op amp both go on and
and follow the instructions there.
and follow the instructions there.
and follow the instructions there.
Hi
If the phase slips are “well behaved” they can be handled. The problem
with a dual channel setup is that they are often not well behaved. The
period is 100 ns so a frequency drift of 1 ppb will put you in trouble in
under 2 minutes.
The only real answer is to do it properly and time tag the two outputs.
Any other approach will get you yelling and screaming at the test set.
Playing with two counters and not time tagging is in the “yelling and
screaming” category as well.
Get a TAPPR TICC if you really want to do a DMTD.
Of course you *could* just use a single mixer. That works fine with the
counter you already have. It will give you an A to B test just like a
DMTD. The only limitation is the need to tune at least one of the oscillators
in each pair.
There is no requirement that you tune only one. If both are tunable,
you could tune one to the high end of its range and the other to the low end.
With most OCXO’s, there is plenty of tune range.
Bob
> On Apr 14, 2020, at 2:23 AM, Tobias Pluess <tpluess@ieee.org> wrote:
>
> Hey Bob
>
> ok now I see your point! you talk about the phase spillovers. Timelab and
> also Stable32 can correct for them, so it shouldn't be a problem, right?
>
> But I agree, if you cannot correct for the spillovers it becomes even more
> difficult.
>
>
> Tobias
>
> On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, <kb8tq@n1k.org> wrote:
>
>> Hi
>>
>> The gotcha with using a conventional counter (as opposed to a time tagger)
>> is that you never know when things are going to “slip” past each other.
>> When they
>> do you get a major burp in your data. Bill’s setup is running a time
>> tagger ….
>>
>> ( = It runs an internal time count, each edge gets “labeled” with a
>> precise time
>> stamp that is good to nanoseconds or picoseconds. A Time Interval Counter
>> simply measures the time between edges. That sounds like the same thing,
>> but
>> it’s not quite ….)
>>
>>
>>> On Apr 13, 2020, at 6:11 PM, Tobias Pluess <tpluess@ieee.org> wrote:
>>>
>>> Hi Bob
>>>
>>> Riley suggests to use a single TIC
>>>
>>> http://wriley.com/A%20Small%20DMTD%20System.pdf
>>>
>>> when you look at the block diagram Fig. 4, you can see that one TIC
>> allows
>>> to compare two oscillators.
>>> I don't know exactly how, though :-)
>>
>> The gotcha with using a conventional counter (as opposed to a time tagger)
>> is that you never know when things are going to “slip” past each other.
>> When they
>> do you get a major burp in your data. Bill’s setup is running a time
>> tagger ….
>>
>>>
>>> OK and I see your point on the 8663. I will try to use another reference!
>>> I definitely didn't keep mine on for a long time. I didn't use the signal
>>> generator for a while now, so it was unplugged for a few months. I assume
>>> that's far from optimal for the 10811's stability.
>>
>> Best approach is to mount your reference off on it’s own and just power
>> it. That way
>> you don’t wear out all the guts of a fancy piece of gear.
>>
>> Bob
>>
>>>
>>>
>>> Tobias
>>>
>>>
>>>
>>> On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote:
>>>
>>>> Hi
>>>>
>>>>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote:
>>>>>
>>>>> Hi Bob
>>>>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
>>>>>
>>>>> Maybe I have some good OpAmps for this purpose in my box. I will try
>> it!
>>>> of
>>>>
>>>> You need something that is quiet (like the OP-37) and has a pretty good
>>>> slew
>>>> rate. Past that, there are a lot of candidates. The TI OPA-228 family is
>>>> one.
>>>>
>>>>> course I saw that my setup was not ideal as there was a bit of noise on
>>>> the
>>>>> signals which I guess does lead to some jitter in the trigger circuit
>> and
>>>>> therefore decreases my measurement noise floor.
>>>>
>>>> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
>>>> digits.
>>>> Net result is a measurement that’s good in the vicinity of parts in
>> 10^-13
>>>>
>>>>>
>>>>> Can you say something about how it would be done using a TIC?
>>>>> I don't have two identically good counters, but the HP 5335A could be
>>>> used
>>>>> as TIC, couldn't it.
>>>>
>>>> The standard way of doing the test is to run two counters / two TIC/s /
>>>> two whatever’s.
>>>> I know of no practical way to do it with a single 5335.
>>>>
>>>>>
>>>>> And the offset source I used is not directly the HP 10811, but the HP
>>>> 8663A
>>>>> Signal generator internally uses a 10811 as reference source. But I
>>>> didn't
>>>>> wait for days for it to warm up properly. (Should I?)
>>>>
>>>> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of
>> how
>>>> you
>>>> use the 10811, it needs to be on for a while. How long very much depends
>>>> on
>>>> just how long it’s been off. Best to keep it on all the time.
>>>>
>>>>>
>>>>>> Fun !!!
>>>>> Yea, of course! :-)
>>>>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
>>>>> myself. I use TimeLab to see what numbers I should expect, and then I
>>>> want
>>>>> to compute it all myself in Matlab because I want to see how it
>> actually
>>>>> works. ;-)
>>>>
>>>> Be careful any time you code this stuff for the first time. It’s
>> amazingly
>>>> easy
>>>> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest
>> that
>>>> you should not code it up yourself. I generally do it in Excel or in C.
>>>>
>>>> Bob
>>>>
>>>>>
>>>>>
>>>>> Best
>>>>> Tobias
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote:
>>>>>
>>>>>> Hi
>>>>>>
>>>>>> Ok, first the math:
>>>>>>
>>>>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
>>>>>>
>>>>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
>>>>>>
>>>>>> You get to add a 6 to what Time Lab shows you.
>>>>>>
>>>>>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
>>>>>> gets you to 1x10^-10
>>>>>>
>>>>>> So, what’s going on?
>>>>>>
>>>>>> You can’t feed the mixer outputs straight into a counter. The counter
>>>>>> front
>>>>>> end does not handle LF audio sine waves very well. You need to do an
>>>>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
>>>>>> similar)
>>>>>> should do the trick.
>>>>>>
>>>>>> Second, the offset source needs to be pretty good. A 10811 tuned high
>>>> with
>>>>>> both the mechanical trim and the EFC is a pretty good choice to start
>>>> out.
>>>>>>
>>>>>> If you only have one counter, simply ignore the second channel. You
>> are
>>>> now
>>>>>> running a single mixer. It still works as a comparison between the
>>>> offset
>>>>>> oscillator
>>>>>> and your DUT.
>>>>>>
>>>>>> If you want to do it properly as a DMTD, then you set up two counters.
>>>> One
>>>>>> to measure mixer A and the other to measure mixer B. Set them both up
>>>> to
>>>>>> measure frequency. Time tag the data files so you know which reading
>>>>>> matches up with which.
>>>>>>
>>>>>> Fun !!!
>>>>>>
>>>>>> Bob
>>>>>>
>>>>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote:
>>>>>>>
>>>>>>> Hi again Bob
>>>>>>>
>>>>>>> I tried to do some measurements with a DMTD!
>>>>>>> In my junk box I found a little PCB from earlier experiments on that
>>>>>> topic,
>>>>>>> with a power splitter and two SRA-3H mixers, it was even already
>> wired
>>>>>> for
>>>>>>> the DMTD configuration. So I gave it a try!
>>>>>>> As "transfer oscillator" I used my HP 8663A signal generator, and set
>>>> it
>>>>>>> high in frequency by 10 Hz. To the two mixers, I connected the two
>>>> 10MHz
>>>>>>> signals and at the mixer outputs, I put a little lowpass filter with
>>>>>> 100Hz
>>>>>>> corner frequency.
>>>>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
>>>>>> tried
>>>>>>> to feed them directly into the HP 5335A TIC and used the TI mode to
>>>>>> measure
>>>>>>> the delay between the two signals.
>>>>>>> This gives 10 readings/sec, which I try to process with TimeLab.
>>>>>>> It does give some interesting graphs, but I don't know yet how to
>>>>>> correctly
>>>>>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV
>> in
>>>>>> the
>>>>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
>> mean
>>>> I
>>>>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at
>> 10MHz?
>>>>>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
>>>>>> which
>>>>>>> is indeed my target value, BUT I expect that things are not that
>>>> simple.
>>>>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but
>>>> only
>>>>>>> by 9.9Hz for example).
>>>>>>> Can you give some hints on that?
>>>>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz
>> signal
>>>>>> into
>>>>>>> a power splitter and connected the two outputs to my DMTD with two
>>>>>>> different lenghts of cables. This gave results starting at 1e-4 going
>>>>>> down
>>>>>>> to 1e-7, maybe it would have gone even lower but I measured only for
>> a
>>>>>>> couple of minutes.)
>>>>>>>
>>>>>>> Can you give some hints on that?
>>>>>>>
>>>>>>> Best
>>>>>>> Tobias
>>>>>>> HB9FSX
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote:
>>>>>>>>
>>>>>>>>> Hi
>>>>>>>>>
>>>>>>>>> The quick way to do this is with a single mixer. Take something
>> like
>>>> an
>>>>>>>>> old
>>>>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to
>> 10
>>>>>> Hz.
>>>>>>>>>
>>>>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
>>>>>> tone.
>>>>>>>>> That tone is the *difference* between the 10811 and your device
>> under
>>>>>>>>> test.
>>>>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
>>>>>>>>>
>>>>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very
>>>> small
>>>>>>>>> shift
>>>>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
>>>>>> change
>>>>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
>>>> increase
>>>>>> ).
>>>>>>>>>
>>>>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no,
>> it’s
>>>>>> not
>>>>>>>>> that
>>>>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
>>>>>>>>> second.
>>>>>>>>>
>>>>>>>>> The reason its not quite that simple is that the input circuit on
>> the
>>>>>>>>> counter
>>>>>>>>> really does not handle a 10 Hz audio tone as well as it handles a
>> 10
>>>>>> MHz
>>>>>>>>> RF signal. Instead of getting 9 digits a second, you probably will
>>>> get
>>>>>>>>> three
>>>>>>>>> *good* digits a second and another 6 digits of noise.
>>>>>>>>>
>>>>>>>>> The good news is that an op amp used as a preamp ( to get you up to
>>>>>> maybe
>>>>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as
>>>>>>>>> limiters will
>>>>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a
>> high
>>>>>> pass
>>>>>>>>> and low pass filter ( DC offsets can be a problem ….) and you have
>> a
>>>>>>>>> working
>>>>>>>>> device that gets into the parts in 10^-13 with your 5335.
>>>>>>>>>
>>>>>>>>> It all can be done with point to point wiring. No need for a PCB
>>>>>> layout.
>>>>>>>>> Be
>>>>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and
>> off
>>>> at
>>>>>>>>> the
>>>>>>>>> same time ….
>>>>>>>>>
>>>>>>>>> Bob
>>>>>>>>>
>>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>>>>>> To unsubscribe, go to
>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>>>>> and follow the instructions there.
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>>>>> To unsubscribe, go to
>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>>>> and follow the instructions there.
>>>>>>
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>>>> To unsubscribe, go to
>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>>> and follow the instructions there.
>>>>
>>>>
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>>> To unsubscribe, go to
>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>> and follow the instructions there.
>>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>> and follow the instructions there.
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts@lists.febo.com
>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
BK
Bob kb8tq
Tue, Apr 14, 2020 11:53 AM
On Apr 14, 2020, at 2:31 AM, Tobias Pluess tpluess@ieee.org wrote:
Hi Taka
good to know you're working on the same stuff :-)
I also think that this is the goal, sort of. But apparently there are some
pitfalls. I hope the experts on this type of measurement (Bob) can give
more hints ;-)
Btw good to know your 10811 took 2 months to settle. In that case I will
try to give mine also more time from power up until I do measurements. But
keeping the 8663 powered on is almost no option for me - my homelab is
simply too small and from time to time I therefore have to tidy it up a bit
and put some of the equipment in another shelf.
You will need the ability to keep stuff on power. That’s true of pretty much
any frequency standard. Indeed the compromise is often made with a Cs
standard since they only have just so many running hours before they
run out of “fuel”. Anything that’s OCXO or Rb based …. leave it on power.
One of the side effects of being locked down is that there is lots of time
to pick up the clutter and really get organized. It’s a amazing just how
many weeks that sort of work has soaked up here :)
Bob
I am working on pretty much the same thing. My HP105B has an HP11801
inside. There is no telling how long it has been off. Frequency wandered
ALL OVER THE PLACE. It took 2 months of continuous operation to settle
down and just do the normal aging/drifting.
I have a same question as you do. How come not just one HP5335? Your
test setup has two output. One goes to start, the other goes to stop.
Measure the time interval. Isn't that the goal?
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Monday, April 13, 2020, 5:53:52 PM EDT, Bob kb8tq <kb8tq@n1k.org>
wrote:
Hi
On Apr 13, 2020, at 5:06 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi Bob
awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
Maybe I have some good OpAmps for this purpose in my box. I will try it!
of
You need something that is quiet (like the OP-37) and has a pretty good
slew
rate. Past that, there are a lot of candidates. The TI OPA-228 family is
one.
course I saw that my setup was not ideal as there was a bit of noise on
signals which I guess does lead to some jitter in the trigger circuit and
therefore decreases my measurement noise floor.
Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
digits.
Net result is a measurement that’s good in the vicinity of parts in 10^-13
Can you say something about how it would be done using a TIC?
I don't have two identically good counters, but the HP 5335A could be
The standard way of doing the test is to run two counters / two TIC/s /
two whatever’s.
I know of no practical way to do it with a single 5335.
And the offset source I used is not directly the HP 10811, but the HP
Signal generator internally uses a 10811 as reference source. But I
wait for days for it to warm up properly. (Should I?)
The 8663 synthesizer adds a lot of crud to the 10811. Regardless of how
you
use the 10811, it needs to be on for a while. How long very much depends
on
just how long it’s been off. Best to keep it on all the time.
Yea, of course! :-)
I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
myself. I use TimeLab to see what numbers I should expect, and then I
to compute it all myself in Matlab because I want to see how it actually
works. ;-)
Be careful any time you code this stuff for the first time. It’s amazingly
easy
( = I’ve done it ….) to make minor errors. That’s in no way to suggest that
you should not code it up yourself. I generally do it in Excel or in C.
Bob
Best
Tobias
On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
Ok, first the math:
If your offset oscillator is 10 Hz high at 10 MHz, you have a:
10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
You get to add a 6 to what Time Lab shows you.
If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
gets you to 1x10^-10
So, what’s going on?
You can’t feed the mixer outputs straight into a counter. The counter
front
end does not handle LF audio sine waves very well. You need to do an
op-amp based limiter. A pair of OP-37’s in each leg ( or something
similar)
should do the trick.
Second, the offset source needs to be pretty good. A 10811 tuned high
both the mechanical trim and the EFC is a pretty good choice to start
If you only have one counter, simply ignore the second channel. You are
running a single mixer. It still works as a comparison between the
oscillator
and your DUT.
If you want to do it properly as a DMTD, then you set up two counters.
to measure mixer A and the other to measure mixer B. Set them both up
measure frequency. Time tag the data files so you know which reading
matches up with which.
Fun !!!
Bob
On Apr 13, 2020, at 3:18 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi again Bob
I tried to do some measurements with a DMTD!
In my junk box I found a little PCB from earlier experiments on that
with a power splitter and two SRA-3H mixers, it was even already wired
the DMTD configuration. So I gave it a try!
As "transfer oscillator" I used my HP 8663A signal generator, and set
high in frequency by 10 Hz. To the two mixers, I connected the two
signals and at the mixer outputs, I put a little lowpass filter with
corner frequency.
The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
to feed them directly into the HP 5335A TIC and used the TI mode to
the delay between the two signals.
This gives 10 readings/sec, which I try to process with TimeLab.
It does give some interesting graphs, but I don't know yet how to
set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in
order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean
simply need to multiply this with 1e-7 to get the real ADEV at 10MHz?
this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
is indeed my target value, BUT I expect that things are not that
(i.e. what if I didn't set the transfer oscillator high by +10Hz but
by 9.9Hz for example).
Can you give some hints on that?
Of course I also did the noise floor test (i.e. I fed the 10MHz signal
a power splitter and connected the two outputs to my DMTD with two
different lenghts of cables. This gave results starting at 1e-4 going
to 1e-7, maybe it would have gone even lower but I measured only for a
couple of minutes.)
Can you give some hints on that?
Best
Tobias
HB9FSX
On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
The quick way to do this is with a single mixer. Take something like
old
10811 and use the coarse tune to set it high in frequency by 5 to 10
Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
That tone is the difference between the 10811 and your device under
test.
If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
If you measured the 10 MHz on the DUT, that 1 Hz would be a very
shift
( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
IF you could tack that on to the ADEV plot of your 5335 ( no, it’s
that
simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
second.
The reason its not quite that simple is that the input circuit on the
counter
really does not handle a 10 Hz audio tone as well as it handles a 10
RF signal. Instead of getting 9 digits a second, you probably will
three
good digits a second and another 6 digits of noise.
The good news is that an op amp used as a preamp ( to get you up to
32 V p-p rather than a volt or so) and another op amp or three as
limiters will
get you up around 6 or 7 good digits. Toss in a cap or two as a high
and low pass filter ( DC offsets can be a problem ….) and you have a
working
device that gets into the parts in 10^-13 with your 5335.
It all can be done with point to point wiring. No need for a PCB
Be
careful that the +/- 18V supplies to the op amp both go on and off
and follow the instructions there.
and follow the instructions there.
Hi
> On Apr 14, 2020, at 2:31 AM, Tobias Pluess <tpluess@ieee.org> wrote:
>
> Hi Taka
> good to know you're working on the same stuff :-)
> I also think that this is the goal, sort of. But apparently there are some
> pitfalls. I hope the experts on this type of measurement (Bob) can give
> more hints ;-)
>
> Btw good to know your 10811 took 2 months to settle. In that case I will
> try to give mine also more time from power up until I do measurements. But
> keeping the 8663 powered on is almost no option for me - my homelab is
> simply too small and from time to time I therefore have to tidy it up a bit
> and put some of the equipment in another shelf.
You will need the ability to keep stuff on power. That’s true of pretty much
any frequency standard. Indeed the compromise is often made with a Cs
standard since they only have just so many running hours before they
run out of “fuel”. Anything that’s OCXO or Rb based …. leave it on power.
One of the side effects of being locked down is that there is *lots* of time
to pick up the clutter and *really* get organized. It’s a amazing just how
many weeks that sort of work has soaked up here :)
Bob
>
>
> Tobias
>
>
> On Tue., 14 Apr. 2020, 01:19 Taka Kamiya via time-nuts, <
> time-nuts@lists.febo.com> wrote:
>
>> I am working on pretty much the same thing. My HP105B has an HP11801
>> inside. There is no telling how long it has been off. Frequency wandered
>> ALL OVER THE PLACE. It took 2 months of continuous operation to settle
>> down and just do the normal aging/drifting.
>>
>> I have a same question as you do. How come not just one HP5335? Your
>> test setup has two output. One goes to start, the other goes to stop.
>> Measure the time interval. Isn't that the goal?
>>
>> ---------------------------------------
>> (Mr.) Taka Kamiya
>> KB4EMF / ex JF2DKG
>>
>>
>> On Monday, April 13, 2020, 5:53:52 PM EDT, Bob kb8tq <kb8tq@n1k.org>
>> wrote:
>>
>> Hi
>>
>>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote:
>>>
>>> Hi Bob
>>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
>>>
>>> Maybe I have some good OpAmps for this purpose in my box. I will try it!
>> of
>>
>> You need something that is quiet (like the OP-37) and has a pretty good
>> slew
>> rate. Past that, there are a lot of candidates. The TI OPA-228 family is
>> one.
>>
>>> course I saw that my setup was not ideal as there was a bit of noise on
>> the
>>> signals which I guess does lead to some jitter in the trigger circuit and
>>> therefore decreases my measurement noise floor.
>>
>> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
>> digits.
>> Net result is a measurement that’s good in the vicinity of parts in 10^-13
>>
>>>
>>> Can you say something about how it would be done using a TIC?
>>> I don't have two identically good counters, but the HP 5335A could be
>> used
>>> as TIC, couldn't it.
>>
>> The standard way of doing the test is to run two counters / two TIC/s /
>> two whatever’s.
>> I know of no practical way to do it with a single 5335.
>>
>>>
>>> And the offset source I used is not directly the HP 10811, but the HP
>> 8663A
>>> Signal generator internally uses a 10811 as reference source. But I
>> didn't
>>> wait for days for it to warm up properly. (Should I?)
>>
>> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of how
>> you
>> use the 10811, it needs to be on for a while. How long very much depends
>> on
>> just how long it’s been off. Best to keep it on all the time.
>>
>>>
>>>> Fun !!!
>>> Yea, of course! :-)
>>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
>>> myself. I use TimeLab to see what numbers I should expect, and then I
>> want
>>> to compute it all myself in Matlab because I want to see how it actually
>>> works. ;-)
>>
>> Be careful any time you code this stuff for the first time. It’s amazingly
>> easy
>> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest that
>> you should not code it up yourself. I generally do it in Excel or in C.
>>
>> Bob
>>
>>>
>>>
>>> Best
>>> Tobias
>>>
>>>
>>>
>>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote:
>>>
>>>> Hi
>>>>
>>>> Ok, first the math:
>>>>
>>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
>>>>
>>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
>>>>
>>>> You get to add a 6 to what Time Lab shows you.
>>>>
>>>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
>>>> gets you to 1x10^-10
>>>>
>>>> So, what’s going on?
>>>>
>>>> You can’t feed the mixer outputs straight into a counter. The counter
>>>> front
>>>> end does not handle LF audio sine waves very well. You need to do an
>>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
>>>> similar)
>>>> should do the trick.
>>>>
>>>> Second, the offset source needs to be pretty good. A 10811 tuned high
>> with
>>>> both the mechanical trim and the EFC is a pretty good choice to start
>> out.
>>>>
>>>> If you only have one counter, simply ignore the second channel. You are
>> now
>>>> running a single mixer. It still works as a comparison between the
>> offset
>>>> oscillator
>>>> and your DUT.
>>>>
>>>> If you want to do it properly as a DMTD, then you set up two counters.
>> One
>>>> to measure mixer A and the other to measure mixer B. Set them both up
>> to
>>>> measure frequency. Time tag the data files so you know which reading
>>>> matches up with which.
>>>>
>>>> Fun !!!
>>>>
>>>> Bob
>>>>
>>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote:
>>>>>
>>>>> Hi again Bob
>>>>>
>>>>> I tried to do some measurements with a DMTD!
>>>>> In my junk box I found a little PCB from earlier experiments on that
>>>> topic,
>>>>> with a power splitter and two SRA-3H mixers, it was even already wired
>>>> for
>>>>> the DMTD configuration. So I gave it a try!
>>>>> As "transfer oscillator" I used my HP 8663A signal generator, and set
>> it
>>>>> high in frequency by 10 Hz. To the two mixers, I connected the two
>> 10MHz
>>>>> signals and at the mixer outputs, I put a little lowpass filter with
>>>> 100Hz
>>>>> corner frequency.
>>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
>>>> tried
>>>>> to feed them directly into the HP 5335A TIC and used the TI mode to
>>>> measure
>>>>> the delay between the two signals.
>>>>> This gives 10 readings/sec, which I try to process with TimeLab.
>>>>> It does give some interesting graphs, but I don't know yet how to
>>>> correctly
>>>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in
>>>> the
>>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean
>> I
>>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz?
>>>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
>>>> which
>>>>> is indeed my target value, BUT I expect that things are not that
>> simple.
>>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but
>> only
>>>>> by 9.9Hz for example).
>>>>> Can you give some hints on that?
>>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz signal
>>>> into
>>>>> a power splitter and connected the two outputs to my DMTD with two
>>>>> different lenghts of cables. This gave results starting at 1e-4 going
>>>> down
>>>>> to 1e-7, maybe it would have gone even lower but I measured only for a
>>>>> couple of minutes.)
>>>>>
>>>>> Can you give some hints on that?
>>>>>
>>>>> Best
>>>>> Tobias
>>>>> HB9FSX
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote:
>>>>>>
>>>>>>> Hi
>>>>>>>
>>>>>>> The quick way to do this is with a single mixer. Take something like
>> an
>>>>>>> old
>>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to 10
>>>> Hz.
>>>>>>>
>>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
>>>> tone.
>>>>>>> That tone is the *difference* between the 10811 and your device under
>>>>>>> test.
>>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
>>>>>>>
>>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very
>> small
>>>>>>> shift
>>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
>>>> change
>>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
>> increase
>>>> ).
>>>>>>>
>>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, it’s
>>>> not
>>>>>>> that
>>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
>>>>>>> second.
>>>>>>>
>>>>>>> The reason its not quite that simple is that the input circuit on the
>>>>>>> counter
>>>>>>> really does not handle a 10 Hz audio tone as well as it handles a 10
>>>> MHz
>>>>>>> RF signal. Instead of getting 9 digits a second, you probably will
>> get
>>>>>>> three
>>>>>>> *good* digits a second and another 6 digits of noise.
>>>>>>>
>>>>>>> The good news is that an op amp used as a preamp ( to get you up to
>>>> maybe
>>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as
>>>>>>> limiters will
>>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a high
>>>> pass
>>>>>>> and low pass filter ( DC offsets can be a problem ….) and you have a
>>>>>>> working
>>>>>>> device that gets into the parts in 10^-13 with your 5335.
>>>>>>>
>>>>>>> It all can be done with point to point wiring. No need for a PCB
>>>> layout.
>>>>>>> Be
>>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and off
>> at
>>>>>>> the
>>>>>>> same time ….
>>>>>>>
>>>>>>> Bob
>>>>>>>
>>>>>>
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>>>> To unsubscribe, go to
>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>>> and follow the instructions there.
>>>>
>>>>
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts@lists.febo.com
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>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>> and follow the instructions there.
>>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>> and follow the instructions there.
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>>
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>> and follow the instructions there.
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>> and follow the instructions there.
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> _______________________________________________
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> and follow the instructions there.
TP
Tobias Pluess
Tue, Apr 14, 2020 12:11 PM
G'day
OK I see I must do it with time tagging :-)
Is it correct that the time tagging just spits out the time (in ns, for
example) when the rising edge on the A or B input occured? and then, you
calculate the phase by subtracting the time tags for the A channel from the
time tags for the B channel?
Riley also says that DMTD works better with time tagging, so I am not
surprised that you recommend it as well. However I hoped that some simple
measurements (only to get a ballpark figure) would be possible with my
current setup.
In fact, since I read the Riley paper about the DMTD system he built, I
have had my own design on my bucket list since quite a while. I planned to
make my own time-tag counter with two TDC7200 as interpolators, to get ps
resolution, very similar to the TAPR TICC.
Tobias
On Tue, Apr 14, 2020 at 1:48 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
If the phase slips are “well behaved” they can be handled. The problem
with a dual channel setup is that they are often not well behaved. The
period is 100 ns so a frequency drift of 1 ppb will put you in trouble in
under 2 minutes.
The only real answer is to do it properly and time tag the two outputs.
Any other approach will get you yelling and screaming at the test set.
Playing with two counters and not time tagging is in the “yelling and
screaming” category as well.
Get a TAPPR TICC if you really want to do a DMTD.
Of course you could just use a single mixer. That works fine with the
counter you already have. It will give you an A to B test just like a
DMTD. The only limitation is the need to tune at least one of the
oscillators
in each pair.
There is no requirement that you tune only one. If both are tunable,
you could tune one to the high end of its range and the other to the low
end.
With most OCXO’s, there is plenty of tune range.
Bob
On Apr 14, 2020, at 2:23 AM, Tobias Pluess tpluess@ieee.org wrote:
Hey Bob
ok now I see your point! you talk about the phase spillovers. Timelab and
also Stable32 can correct for them, so it shouldn't be a problem, right?
But I agree, if you cannot correct for the spillovers it becomes even
difficult.
Tobias
On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, kb8tq@n1k.org wrote:
Hi
The gotcha with using a conventional counter (as opposed to a time
is that you never know when things are going to “slip” past each other.
When they
do you get a major burp in your data. Bill’s setup is running a time
tagger ….
( = It runs an internal time count, each edge gets “labeled” with a
precise time
stamp that is good to nanoseconds or picoseconds. A Time Interval
simply measures the time between edges. That sounds like the same thing,
but
it’s not quite ….)
to compare two oscillators.
I don't know exactly how, though :-)
The gotcha with using a conventional counter (as opposed to a time
is that you never know when things are going to “slip” past each other.
When they
do you get a major burp in your data. Bill’s setup is running a time
tagger ….
OK and I see your point on the 8663. I will try to use another
I definitely didn't keep mine on for a long time. I didn't use the
generator for a while now, so it was unplugged for a few months. I
that's far from optimal for the 10811's stability.
Best approach is to mount your reference off on it’s own and just power
it. That way
you don’t wear out all the guts of a fancy piece of gear.
Bob
Tobias
On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, kb8tq@n1k.org wrote:
On Apr 13, 2020, at 5:06 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi Bob
awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
Maybe I have some good OpAmps for this purpose in my box. I will try
of
You need something that is quiet (like the OP-37) and has a pretty
slew
rate. Past that, there are a lot of candidates. The TI OPA-228 family
course I saw that my setup was not ideal as there was a bit of noise
signals which I guess does lead to some jitter in the trigger circuit
therefore decreases my measurement noise floor.
Typically a good limiter takes you from 3 or 4 digits up to 6 or 7
digits.
Net result is a measurement that’s good in the vicinity of parts in
Can you say something about how it would be done using a TIC?
I don't have two identically good counters, but the HP 5335A could be
The standard way of doing the test is to run two counters / two TIC/s
two whatever’s.
I know of no practical way to do it with a single 5335.
And the offset source I used is not directly the HP 10811, but the HP
Signal generator internally uses a 10811 as reference source. But I
wait for days for it to warm up properly. (Should I?)
The 8663 synthesizer adds a lot of crud to the 10811. Regardless of
you
use the 10811, it needs to be on for a while. How long very much
on
just how long it’s been off. Best to keep it on all the time.
Yea, of course! :-)
I already implemented the ADEV, MDEV and TDEV calculations in Matlab
myself. I use TimeLab to see what numbers I should expect, and then I
to compute it all myself in Matlab because I want to see how it
Be careful any time you code this stuff for the first time. It’s
easy
( = I’ve done it ….) to make minor errors. That’s in no way to suggest
you should not code it up yourself. I generally do it in Excel or in
Best
Tobias
On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
Ok, first the math:
If your offset oscillator is 10 Hz high at 10 MHz, you have a:
10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
You get to add a 6 to what Time Lab shows you.
If you are getting an ADEV at 1 second of 1x10^-4 then that
gets you to 1x10^-10
So, what’s going on?
You can’t feed the mixer outputs straight into a counter. The
front
end does not handle LF audio sine waves very well. You need to do an
op-amp based limiter. A pair of OP-37’s in each leg ( or something
similar)
should do the trick.
Second, the offset source needs to be pretty good. A 10811 tuned
both the mechanical trim and the EFC is a pretty good choice to
If you only have one counter, simply ignore the second channel. You
running a single mixer. It still works as a comparison between the
oscillator
and your DUT.
If you want to do it properly as a DMTD, then you set up two
to measure mixer A and the other to measure mixer B. Set them both
measure frequency. Time tag the data files so you know which reading
matches up with which.
Fun !!!
Bob
Hi again Bob
I tried to do some measurements with a DMTD!
In my junk box I found a little PCB from earlier experiments on
with a power splitter and two SRA-3H mixers, it was even already
the DMTD configuration. So I gave it a try!
As "transfer oscillator" I used my HP 8663A signal generator, and
high in frequency by 10 Hz. To the two mixers, I connected the two
signals and at the mixer outputs, I put a little lowpass filter
corner frequency.
The output signals from the two SRA-3 mixers are almost 0.5Vpp, so
to feed them directly into the HP 5335A TIC and used the TI mode to
the delay between the two signals.
This gives 10 readings/sec, which I try to process with TimeLab.
It does give some interesting graphs, but I don't know yet how to
set up TimeLab for this kind of measurement. I.e. now, I get an
order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
simply need to multiply this with 1e-7 to get the real ADEV at
this would mean that my real ADEV is in the range of 1e-11 to
is indeed my target value, BUT I expect that things are not that
(i.e. what if I didn't set the transfer oscillator high by +10Hz
by 9.9Hz for example).
Can you give some hints on that?
Of course I also did the noise floor test (i.e. I fed the 10MHz
a power splitter and connected the two outputs to my DMTD with two
different lenghts of cables. This gave results starting at 1e-4
to 1e-7, maybe it would have gone even lower but I measured only
couple of minutes.)
Can you give some hints on that?
Best
Tobias
HB9FSX
On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
The quick way to do this is with a single mixer. Take something
old
10811 and use the coarse tune to set it high in frequency by 5 to
Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz
That tone is the difference between the 10811 and your device
test.
If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
If you measured the 10 MHz on the DUT, that 1 Hz would be a very
shift
( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
IF you could tack that on to the ADEV plot of your 5335 ( no,
that
simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
second.
The reason its not quite that simple is that the input circuit on
counter
really does not handle a 10 Hz audio tone as well as it handles a
RF signal. Instead of getting 9 digits a second, you probably
three
good digits a second and another 6 digits of noise.
The good news is that an op amp used as a preamp ( to get you up
32 V p-p rather than a volt or so) and another op amp or three as
limiters will
get you up around 6 or 7 good digits. Toss in a cap or two as a
and low pass filter ( DC offsets can be a problem ….) and you
working
device that gets into the parts in 10^-13 with your 5335.
It all can be done with point to point wiring. No need for a PCB
Be
careful that the +/- 18V supplies to the op amp both go on and
and follow the instructions there.
and follow the instructions there.
and follow the instructions there.
and follow the instructions there.
G'day
OK I see I must do it with time tagging :-)
Is it correct that the time tagging just spits out the time (in ns, for
example) when the rising edge on the A or B input occured? and then, you
calculate the phase by subtracting the time tags for the A channel from the
time tags for the B channel?
Riley also says that DMTD works better with time tagging, so I am not
surprised that you recommend it as well. However I hoped that some simple
measurements (only to get a ballpark figure) would be possible with my
current setup.
In fact, since I read the Riley paper about the DMTD system he built, I
have had my own design on my bucket list since quite a while. I planned to
make my own time-tag counter with two TDC7200 as interpolators, to get ps
resolution, very similar to the TAPR TICC.
Tobias
On Tue, Apr 14, 2020 at 1:48 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> Hi
>
> If the phase slips are “well behaved” they can be handled. The problem
> with a dual channel setup is that they are often not well behaved. The
> period is 100 ns so a frequency drift of 1 ppb will put you in trouble in
> under 2 minutes.
>
> The only real answer is to do it properly and time tag the two outputs.
> Any other approach will get you yelling and screaming at the test set.
> Playing with two counters and not time tagging is in the “yelling and
> screaming” category as well.
>
> Get a TAPPR TICC if you really want to do a DMTD.
>
> Of course you *could* just use a single mixer. That works fine with the
> counter you already have. It will give you an A to B test just like a
> DMTD. The only limitation is the need to tune at least one of the
> oscillators
> in each pair.
>
> There is no requirement that you tune only one. If both are tunable,
> you could tune one to the high end of its range and the other to the low
> end.
> With most OCXO’s, there is plenty of tune range.
>
> Bob
>
> > On Apr 14, 2020, at 2:23 AM, Tobias Pluess <tpluess@ieee.org> wrote:
> >
> > Hey Bob
> >
> > ok now I see your point! you talk about the phase spillovers. Timelab and
> > also Stable32 can correct for them, so it shouldn't be a problem, right?
> >
> > But I agree, if you cannot correct for the spillovers it becomes even
> more
> > difficult.
> >
> >
> > Tobias
> >
> > On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, <kb8tq@n1k.org> wrote:
> >
> >> Hi
> >>
> >> The gotcha with using a conventional counter (as opposed to a time
> tagger)
> >> is that you never know when things are going to “slip” past each other.
> >> When they
> >> do you get a major burp in your data. Bill’s setup is running a time
> >> tagger ….
> >>
> >> ( = It runs an internal time count, each edge gets “labeled” with a
> >> precise time
> >> stamp that is good to nanoseconds or picoseconds. A Time Interval
> Counter
> >> simply measures the time between edges. That sounds like the same thing,
> >> but
> >> it’s not quite ….)
> >>
> >>
> >>> On Apr 13, 2020, at 6:11 PM, Tobias Pluess <tpluess@ieee.org> wrote:
> >>>
> >>> Hi Bob
> >>>
> >>> Riley suggests to use a single TIC
> >>>
> >>> http://wriley.com/A%20Small%20DMTD%20System.pdf
> >>>
> >>> when you look at the block diagram Fig. 4, you can see that one TIC
> >> allows
> >>> to compare two oscillators.
> >>> I don't know exactly how, though :-)
> >>
> >> The gotcha with using a conventional counter (as opposed to a time
> tagger)
> >> is that you never know when things are going to “slip” past each other.
> >> When they
> >> do you get a major burp in your data. Bill’s setup is running a time
> >> tagger ….
> >>
> >>>
> >>> OK and I see your point on the 8663. I will try to use another
> reference!
> >>> I definitely didn't keep mine on for a long time. I didn't use the
> signal
> >>> generator for a while now, so it was unplugged for a few months. I
> assume
> >>> that's far from optimal for the 10811's stability.
> >>
> >> Best approach is to mount your reference off on it’s own and just power
> >> it. That way
> >> you don’t wear out all the guts of a fancy piece of gear.
> >>
> >> Bob
> >>
> >>>
> >>>
> >>> Tobias
> >>>
> >>>
> >>>
> >>> On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote:
> >>>
> >>>> Hi
> >>>>
> >>>>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote:
> >>>>>
> >>>>> Hi Bob
> >>>>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
> >>>>>
> >>>>> Maybe I have some good OpAmps for this purpose in my box. I will try
> >> it!
> >>>> of
> >>>>
> >>>> You need something that is quiet (like the OP-37) and has a pretty
> good
> >>>> slew
> >>>> rate. Past that, there are a lot of candidates. The TI OPA-228 family
> is
> >>>> one.
> >>>>
> >>>>> course I saw that my setup was not ideal as there was a bit of noise
> on
> >>>> the
> >>>>> signals which I guess does lead to some jitter in the trigger circuit
> >> and
> >>>>> therefore decreases my measurement noise floor.
> >>>>
> >>>> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7
> good
> >>>> digits.
> >>>> Net result is a measurement that’s good in the vicinity of parts in
> >> 10^-13
> >>>>
> >>>>>
> >>>>> Can you say something about how it would be done using a TIC?
> >>>>> I don't have two identically good counters, but the HP 5335A could be
> >>>> used
> >>>>> as TIC, couldn't it.
> >>>>
> >>>> The standard way of doing the test is to run two counters / two TIC/s
> /
> >>>> two whatever’s.
> >>>> I know of no practical way to do it with a single 5335.
> >>>>
> >>>>>
> >>>>> And the offset source I used is not directly the HP 10811, but the HP
> >>>> 8663A
> >>>>> Signal generator internally uses a 10811 as reference source. But I
> >>>> didn't
> >>>>> wait for days for it to warm up properly. (Should I?)
> >>>>
> >>>> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of
> >> how
> >>>> you
> >>>> use the 10811, it needs to be on for a while. How long very much
> depends
> >>>> on
> >>>> just how long it’s been off. Best to keep it on all the time.
> >>>>
> >>>>>
> >>>>>> Fun !!!
> >>>>> Yea, of course! :-)
> >>>>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab
> by
> >>>>> myself. I use TimeLab to see what numbers I should expect, and then I
> >>>> want
> >>>>> to compute it all myself in Matlab because I want to see how it
> >> actually
> >>>>> works. ;-)
> >>>>
> >>>> Be careful any time you code this stuff for the first time. It’s
> >> amazingly
> >>>> easy
> >>>> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest
> >> that
> >>>> you should not code it up yourself. I generally do it in Excel or in
> C.
> >>>>
> >>>> Bob
> >>>>
> >>>>>
> >>>>>
> >>>>> Best
> >>>>> Tobias
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >>>>>
> >>>>>> Hi
> >>>>>>
> >>>>>> Ok, first the math:
> >>>>>>
> >>>>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
> >>>>>>
> >>>>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
> >>>>>>
> >>>>>> You get to add a 6 to what Time Lab shows you.
> >>>>>>
> >>>>>> If you are getting an ADEV at 1 second of 1x10^-4 then that
> multiplier
> >>>>>> gets you to 1x10^-10
> >>>>>>
> >>>>>> So, what’s going on?
> >>>>>>
> >>>>>> You can’t feed the mixer outputs straight into a counter. The
> counter
> >>>>>> front
> >>>>>> end does not handle LF audio sine waves very well. You need to do an
> >>>>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
> >>>>>> similar)
> >>>>>> should do the trick.
> >>>>>>
> >>>>>> Second, the offset source needs to be pretty good. A 10811 tuned
> high
> >>>> with
> >>>>>> both the mechanical trim and the EFC is a pretty good choice to
> start
> >>>> out.
> >>>>>>
> >>>>>> If you only have one counter, simply ignore the second channel. You
> >> are
> >>>> now
> >>>>>> running a single mixer. It still works as a comparison between the
> >>>> offset
> >>>>>> oscillator
> >>>>>> and your DUT.
> >>>>>>
> >>>>>> If you want to do it properly as a DMTD, then you set up two
> counters.
> >>>> One
> >>>>>> to measure mixer A and the other to measure mixer B. Set them both
> up
> >>>> to
> >>>>>> measure frequency. Time tag the data files so you know which reading
> >>>>>> matches up with which.
> >>>>>>
> >>>>>> Fun !!!
> >>>>>>
> >>>>>> Bob
> >>>>>>
> >>>>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org>
> wrote:
> >>>>>>>
> >>>>>>> Hi again Bob
> >>>>>>>
> >>>>>>> I tried to do some measurements with a DMTD!
> >>>>>>> In my junk box I found a little PCB from earlier experiments on
> that
> >>>>>> topic,
> >>>>>>> with a power splitter and two SRA-3H mixers, it was even already
> >> wired
> >>>>>> for
> >>>>>>> the DMTD configuration. So I gave it a try!
> >>>>>>> As "transfer oscillator" I used my HP 8663A signal generator, and
> set
> >>>> it
> >>>>>>> high in frequency by 10 Hz. To the two mixers, I connected the two
> >>>> 10MHz
> >>>>>>> signals and at the mixer outputs, I put a little lowpass filter
> with
> >>>>>> 100Hz
> >>>>>>> corner frequency.
> >>>>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so
> I
> >>>>>> tried
> >>>>>>> to feed them directly into the HP 5335A TIC and used the TI mode to
> >>>>>> measure
> >>>>>>> the delay between the two signals.
> >>>>>>> This gives 10 readings/sec, which I try to process with TimeLab.
> >>>>>>> It does give some interesting graphs, but I don't know yet how to
> >>>>>> correctly
> >>>>>>> set up TimeLab for this kind of measurement. I.e. now, I get an
> ADEV
> >> in
> >>>>>> the
> >>>>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
> >> mean
> >>>> I
> >>>>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at
> >> 10MHz?
> >>>>>>> this would mean that my real ADEV is in the range of 1e-11 to
> 1e-12,
> >>>>>> which
> >>>>>>> is indeed my target value, BUT I expect that things are not that
> >>>> simple.
> >>>>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz
> but
> >>>> only
> >>>>>>> by 9.9Hz for example).
> >>>>>>> Can you give some hints on that?
> >>>>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz
> >> signal
> >>>>>> into
> >>>>>>> a power splitter and connected the two outputs to my DMTD with two
> >>>>>>> different lenghts of cables. This gave results starting at 1e-4
> going
> >>>>>> down
> >>>>>>> to 1e-7, maybe it would have gone even lower but I measured only
> for
> >> a
> >>>>>>> couple of minutes.)
> >>>>>>>
> >>>>>>> Can you give some hints on that?
> >>>>>>>
> >>>>>>> Best
> >>>>>>> Tobias
> >>>>>>> HB9FSX
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >>>>>>>>
> >>>>>>>>> Hi
> >>>>>>>>>
> >>>>>>>>> The quick way to do this is with a single mixer. Take something
> >> like
> >>>> an
> >>>>>>>>> old
> >>>>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to
> >> 10
> >>>>>> Hz.
> >>>>>>>>>
> >>>>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz
> audio
> >>>>>> tone.
> >>>>>>>>> That tone is the *difference* between the 10811 and your device
> >> under
> >>>>>>>>> test.
> >>>>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
> >>>>>>>>>
> >>>>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very
> >>>> small
> >>>>>>>>> shift
> >>>>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
> >>>>>> change
> >>>>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
> >>>> increase
> >>>>>> ).
> >>>>>>>>>
> >>>>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no,
> >> it’s
> >>>>>> not
> >>>>>>>>> that
> >>>>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
> >>>>>>>>> second.
> >>>>>>>>>
> >>>>>>>>> The reason its not quite that simple is that the input circuit on
> >> the
> >>>>>>>>> counter
> >>>>>>>>> really does not handle a 10 Hz audio tone as well as it handles a
> >> 10
> >>>>>> MHz
> >>>>>>>>> RF signal. Instead of getting 9 digits a second, you probably
> will
> >>>> get
> >>>>>>>>> three
> >>>>>>>>> *good* digits a second and another 6 digits of noise.
> >>>>>>>>>
> >>>>>>>>> The good news is that an op amp used as a preamp ( to get you up
> to
> >>>>>> maybe
> >>>>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as
> >>>>>>>>> limiters will
> >>>>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a
> >> high
> >>>>>> pass
> >>>>>>>>> and low pass filter ( DC offsets can be a problem ….) and you
> have
> >> a
> >>>>>>>>> working
> >>>>>>>>> device that gets into the parts in 10^-13 with your 5335.
> >>>>>>>>>
> >>>>>>>>> It all can be done with point to point wiring. No need for a PCB
> >>>>>> layout.
> >>>>>>>>> Be
> >>>>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and
> >> off
> >>>> at
> >>>>>>>>> the
> >>>>>>>>> same time ….
> >>>>>>>>>
> >>>>>>>>> Bob
> >>>>>>>>>
> >>>>>>>>
> >>>>>>> _______________________________________________
> >>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>>>>>> To unsubscribe, go to
> >>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>>>>>> and follow the instructions there.
> >>>>>>
> >>>>>>
> >>>>>> _______________________________________________
> >>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>>>>> To unsubscribe, go to
> >>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>>>>> and follow the instructions there.
> >>>>>>
> >>>>> _______________________________________________
> >>>>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>>>> To unsubscribe, go to
> >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>>>> and follow the instructions there.
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>>> To unsubscribe, go to
> >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>>> and follow the instructions there.
> >>>>
> >>> _______________________________________________
> >>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>> and follow the instructions there.
> >>
> >>
> >> _______________________________________________
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >>
> > _______________________________________________
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
TP
Tobias Pluess
Tue, Apr 14, 2020 12:15 PM
Hi Bob
yes sure I know. At least my homebrew GPSDO and the STAR4 GPSDO I have are
always powered, but since they don't take much space on my desk that's
okay. But for the signal generators (or SpecAn etc) it is a completely
different story; I usually take them from the shelf when I need them and
put them back afterwards, because they simply take too much space away. And
my home lab has only limited space, unfortunately. I am thinking since
months about a better setup (how arrange everything, how to stack my
equipment and such) but it is not so easy because simply stacking all
equipment on top of each other is unsatisfactory (in that case one needs in
general the instrument at the very top, which is simply too far away :-)).
The 8663A is a nice machine, but it would fill my desk already by 50%, so
no way to leave it there (and therefore I cannot keep it powered).
Tobias
On Tue, Apr 14, 2020 at 1:54 PM Bob kb8tq kb8tq@n1k.org wrote:
On Apr 14, 2020, at 2:31 AM, Tobias Pluess tpluess@ieee.org wrote:
Hi Taka
good to know you're working on the same stuff :-)
I also think that this is the goal, sort of. But apparently there are
pitfalls. I hope the experts on this type of measurement (Bob) can give
more hints ;-)
Btw good to know your 10811 took 2 months to settle. In that case I will
try to give mine also more time from power up until I do measurements.
keeping the 8663 powered on is almost no option for me - my homelab is
simply too small and from time to time I therefore have to tidy it up a
and put some of the equipment in another shelf.
You will need the ability to keep stuff on power. That’s true of pretty
much
any frequency standard. Indeed the compromise is often made with a Cs
standard since they only have just so many running hours before they
run out of “fuel”. Anything that’s OCXO or Rb based …. leave it on power.
One of the side effects of being locked down is that there is lots of
time
to pick up the clutter and really get organized. It’s a amazing just how
many weeks that sort of work has soaked up here :)
Bob
I am working on pretty much the same thing. My HP105B has an HP11801
inside. There is no telling how long it has been off. Frequency
ALL OVER THE PLACE. It took 2 months of continuous operation to settle
down and just do the normal aging/drifting.
I have a same question as you do. How come not just one HP5335? Your
test setup has two output. One goes to start, the other goes to stop.
Measure the time interval. Isn't that the goal?
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Monday, April 13, 2020, 5:53:52 PM EDT, Bob kb8tq <kb8tq@n1k.org>
wrote:
Hi
On Apr 13, 2020, at 5:06 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi Bob
awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
Maybe I have some good OpAmps for this purpose in my box. I will try
of
You need something that is quiet (like the OP-37) and has a pretty good
slew
rate. Past that, there are a lot of candidates. The TI OPA-228 family is
one.
course I saw that my setup was not ideal as there was a bit of noise on
signals which I guess does lead to some jitter in the trigger circuit
therefore decreases my measurement noise floor.
Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
digits.
Net result is a measurement that’s good in the vicinity of parts in
Can you say something about how it would be done using a TIC?
I don't have two identically good counters, but the HP 5335A could be
The standard way of doing the test is to run two counters / two TIC/s /
two whatever’s.
I know of no practical way to do it with a single 5335.
And the offset source I used is not directly the HP 10811, but the HP
Signal generator internally uses a 10811 as reference source. But I
wait for days for it to warm up properly. (Should I?)
The 8663 synthesizer adds a lot of crud to the 10811. Regardless of
you
use the 10811, it needs to be on for a while. How long very much depends
on
just how long it’s been off. Best to keep it on all the time.
Yea, of course! :-)
I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
myself. I use TimeLab to see what numbers I should expect, and then I
to compute it all myself in Matlab because I want to see how it
Be careful any time you code this stuff for the first time. It’s
easy
( = I’ve done it ….) to make minor errors. That’s in no way to suggest
you should not code it up yourself. I generally do it in Excel or in C.
Bob
Best
Tobias
On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
Ok, first the math:
If your offset oscillator is 10 Hz high at 10 MHz, you have a:
10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
You get to add a 6 to what Time Lab shows you.
If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
gets you to 1x10^-10
So, what’s going on?
You can’t feed the mixer outputs straight into a counter. The counter
front
end does not handle LF audio sine waves very well. You need to do an
op-amp based limiter. A pair of OP-37’s in each leg ( or something
similar)
should do the trick.
Second, the offset source needs to be pretty good. A 10811 tuned high
both the mechanical trim and the EFC is a pretty good choice to start
If you only have one counter, simply ignore the second channel. You
running a single mixer. It still works as a comparison between the
oscillator
and your DUT.
If you want to do it properly as a DMTD, then you set up two counters.
to measure mixer A and the other to measure mixer B. Set them both up
measure frequency. Time tag the data files so you know which reading
matches up with which.
Fun !!!
Bob
On Apr 13, 2020, at 3:18 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi again Bob
I tried to do some measurements with a DMTD!
In my junk box I found a little PCB from earlier experiments on that
with a power splitter and two SRA-3H mixers, it was even already
the DMTD configuration. So I gave it a try!
As "transfer oscillator" I used my HP 8663A signal generator, and set
high in frequency by 10 Hz. To the two mixers, I connected the two
signals and at the mixer outputs, I put a little lowpass filter with
corner frequency.
The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
to feed them directly into the HP 5335A TIC and used the TI mode to
the delay between the two signals.
This gives 10 readings/sec, which I try to process with TimeLab.
It does give some interesting graphs, but I don't know yet how to
set up TimeLab for this kind of measurement. I.e. now, I get an ADEV
order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
simply need to multiply this with 1e-7 to get the real ADEV at
this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
is indeed my target value, BUT I expect that things are not that
(i.e. what if I didn't set the transfer oscillator high by +10Hz but
by 9.9Hz for example).
Can you give some hints on that?
Of course I also did the noise floor test (i.e. I fed the 10MHz
a power splitter and connected the two outputs to my DMTD with two
different lenghts of cables. This gave results starting at 1e-4 going
to 1e-7, maybe it would have gone even lower but I measured only for
couple of minutes.)
Can you give some hints on that?
Best
Tobias
HB9FSX
On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
The quick way to do this is with a single mixer. Take something
old
10811 and use the coarse tune to set it high in frequency by 5 to
Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
That tone is the difference between the 10811 and your device
test.
If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
If you measured the 10 MHz on the DUT, that 1 Hz would be a very
shift
( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
IF you could tack that on to the ADEV plot of your 5335 ( no,
that
simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
second.
The reason its not quite that simple is that the input circuit on
counter
really does not handle a 10 Hz audio tone as well as it handles a
RF signal. Instead of getting 9 digits a second, you probably will
three
good digits a second and another 6 digits of noise.
The good news is that an op amp used as a preamp ( to get you up to
32 V p-p rather than a volt or so) and another op amp or three as
limiters will
get you up around 6 or 7 good digits. Toss in a cap or two as a
and low pass filter ( DC offsets can be a problem ….) and you have
working
device that gets into the parts in 10^-13 with your 5335.
It all can be done with point to point wiring. No need for a PCB
Be
careful that the +/- 18V supplies to the op amp both go on and
and follow the instructions there.
and follow the instructions there.
and follow the instructions there.
Hi Bob
yes sure I know. At least my homebrew GPSDO and the STAR4 GPSDO I have are
always powered, but since they don't take much space on my desk that's
okay. But for the signal generators (or SpecAn etc) it is a completely
different story; I usually take them from the shelf when I need them and
put them back afterwards, because they simply take too much space away. And
my home lab has only limited space, unfortunately. I am thinking since
months about a better setup (how arrange everything, how to stack my
equipment and such) but it is not so easy because simply stacking all
equipment on top of each other is unsatisfactory (in that case one needs in
general the instrument at the very top, which is simply too far away :-)).
The 8663A is a nice machine, but it would fill my desk already by 50%, so
no way to leave it there (and therefore I cannot keep it powered).
Tobias
On Tue, Apr 14, 2020 at 1:54 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> Hi
>
> > On Apr 14, 2020, at 2:31 AM, Tobias Pluess <tpluess@ieee.org> wrote:
> >
> > Hi Taka
> > good to know you're working on the same stuff :-)
> > I also think that this is the goal, sort of. But apparently there are
> some
> > pitfalls. I hope the experts on this type of measurement (Bob) can give
> > more hints ;-)
> >
> > Btw good to know your 10811 took 2 months to settle. In that case I will
> > try to give mine also more time from power up until I do measurements.
> But
> > keeping the 8663 powered on is almost no option for me - my homelab is
> > simply too small and from time to time I therefore have to tidy it up a
> bit
> > and put some of the equipment in another shelf.
>
> You will need the ability to keep stuff on power. That’s true of pretty
> much
> any frequency standard. Indeed the compromise is often made with a Cs
> standard since they only have just so many running hours before they
> run out of “fuel”. Anything that’s OCXO or Rb based …. leave it on power.
>
> One of the side effects of being locked down is that there is *lots* of
> time
> to pick up the clutter and *really* get organized. It’s a amazing just how
> many weeks that sort of work has soaked up here :)
>
> Bob
>
> >
> >
> > Tobias
> >
> >
> > On Tue., 14 Apr. 2020, 01:19 Taka Kamiya via time-nuts, <
> > time-nuts@lists.febo.com> wrote:
> >
> >> I am working on pretty much the same thing. My HP105B has an HP11801
> >> inside. There is no telling how long it has been off. Frequency
> wandered
> >> ALL OVER THE PLACE. It took 2 months of continuous operation to settle
> >> down and just do the normal aging/drifting.
> >>
> >> I have a same question as you do. How come not just one HP5335? Your
> >> test setup has two output. One goes to start, the other goes to stop.
> >> Measure the time interval. Isn't that the goal?
> >>
> >> ---------------------------------------
> >> (Mr.) Taka Kamiya
> >> KB4EMF / ex JF2DKG
> >>
> >>
> >> On Monday, April 13, 2020, 5:53:52 PM EDT, Bob kb8tq <kb8tq@n1k.org>
> >> wrote:
> >>
> >> Hi
> >>
> >>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote:
> >>>
> >>> Hi Bob
> >>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
> >>>
> >>> Maybe I have some good OpAmps for this purpose in my box. I will try
> it!
> >> of
> >>
> >> You need something that is quiet (like the OP-37) and has a pretty good
> >> slew
> >> rate. Past that, there are a lot of candidates. The TI OPA-228 family is
> >> one.
> >>
> >>> course I saw that my setup was not ideal as there was a bit of noise on
> >> the
> >>> signals which I guess does lead to some jitter in the trigger circuit
> and
> >>> therefore decreases my measurement noise floor.
> >>
> >> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good
> >> digits.
> >> Net result is a measurement that’s good in the vicinity of parts in
> 10^-13
> >>
> >>>
> >>> Can you say something about how it would be done using a TIC?
> >>> I don't have two identically good counters, but the HP 5335A could be
> >> used
> >>> as TIC, couldn't it.
> >>
> >> The standard way of doing the test is to run two counters / two TIC/s /
> >> two whatever’s.
> >> I know of no practical way to do it with a single 5335.
> >>
> >>>
> >>> And the offset source I used is not directly the HP 10811, but the HP
> >> 8663A
> >>> Signal generator internally uses a 10811 as reference source. But I
> >> didn't
> >>> wait for days for it to warm up properly. (Should I?)
> >>
> >> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of
> how
> >> you
> >> use the 10811, it needs to be on for a while. How long very much depends
> >> on
> >> just how long it’s been off. Best to keep it on all the time.
> >>
> >>>
> >>>> Fun !!!
> >>> Yea, of course! :-)
> >>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by
> >>> myself. I use TimeLab to see what numbers I should expect, and then I
> >> want
> >>> to compute it all myself in Matlab because I want to see how it
> actually
> >>> works. ;-)
> >>
> >> Be careful any time you code this stuff for the first time. It’s
> amazingly
> >> easy
> >> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest
> that
> >> you should not code it up yourself. I generally do it in Excel or in C.
> >>
> >> Bob
> >>
> >>>
> >>>
> >>> Best
> >>> Tobias
> >>>
> >>>
> >>>
> >>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >>>
> >>>> Hi
> >>>>
> >>>> Ok, first the math:
> >>>>
> >>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
> >>>>
> >>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
> >>>>
> >>>> You get to add a 6 to what Time Lab shows you.
> >>>>
> >>>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier
> >>>> gets you to 1x10^-10
> >>>>
> >>>> So, what’s going on?
> >>>>
> >>>> You can’t feed the mixer outputs straight into a counter. The counter
> >>>> front
> >>>> end does not handle LF audio sine waves very well. You need to do an
> >>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
> >>>> similar)
> >>>> should do the trick.
> >>>>
> >>>> Second, the offset source needs to be pretty good. A 10811 tuned high
> >> with
> >>>> both the mechanical trim and the EFC is a pretty good choice to start
> >> out.
> >>>>
> >>>> If you only have one counter, simply ignore the second channel. You
> are
> >> now
> >>>> running a single mixer. It still works as a comparison between the
> >> offset
> >>>> oscillator
> >>>> and your DUT.
> >>>>
> >>>> If you want to do it properly as a DMTD, then you set up two counters.
> >> One
> >>>> to measure mixer A and the other to measure mixer B. Set them both up
> >> to
> >>>> measure frequency. Time tag the data files so you know which reading
> >>>> matches up with which.
> >>>>
> >>>> Fun !!!
> >>>>
> >>>> Bob
> >>>>
> >>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote:
> >>>>>
> >>>>> Hi again Bob
> >>>>>
> >>>>> I tried to do some measurements with a DMTD!
> >>>>> In my junk box I found a little PCB from earlier experiments on that
> >>>> topic,
> >>>>> with a power splitter and two SRA-3H mixers, it was even already
> wired
> >>>> for
> >>>>> the DMTD configuration. So I gave it a try!
> >>>>> As "transfer oscillator" I used my HP 8663A signal generator, and set
> >> it
> >>>>> high in frequency by 10 Hz. To the two mixers, I connected the two
> >> 10MHz
> >>>>> signals and at the mixer outputs, I put a little lowpass filter with
> >>>> 100Hz
> >>>>> corner frequency.
> >>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I
> >>>> tried
> >>>>> to feed them directly into the HP 5335A TIC and used the TI mode to
> >>>> measure
> >>>>> the delay between the two signals.
> >>>>> This gives 10 readings/sec, which I try to process with TimeLab.
> >>>>> It does give some interesting graphs, but I don't know yet how to
> >>>> correctly
> >>>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV
> in
> >>>> the
> >>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
> mean
> >> I
> >>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at
> 10MHz?
> >>>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12,
> >>>> which
> >>>>> is indeed my target value, BUT I expect that things are not that
> >> simple.
> >>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but
> >> only
> >>>>> by 9.9Hz for example).
> >>>>> Can you give some hints on that?
> >>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz
> signal
> >>>> into
> >>>>> a power splitter and connected the two outputs to my DMTD with two
> >>>>> different lenghts of cables. This gave results starting at 1e-4 going
> >>>> down
> >>>>> to 1e-7, maybe it would have gone even lower but I measured only for
> a
> >>>>> couple of minutes.)
> >>>>>
> >>>>> Can you give some hints on that?
> >>>>>
> >>>>> Best
> >>>>> Tobias
> >>>>> HB9FSX
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >>>>>>
> >>>>>>> Hi
> >>>>>>>
> >>>>>>> The quick way to do this is with a single mixer. Take something
> like
> >> an
> >>>>>>> old
> >>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to
> 10
> >>>> Hz.
> >>>>>>>
> >>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio
> >>>> tone.
> >>>>>>> That tone is the *difference* between the 10811 and your device
> under
> >>>>>>> test.
> >>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
> >>>>>>>
> >>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very
> >> small
> >>>>>>> shift
> >>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
> >>>> change
> >>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
> >> increase
> >>>> ).
> >>>>>>>
> >>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no,
> it’s
> >>>> not
> >>>>>>> that
> >>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
> >>>>>>> second.
> >>>>>>>
> >>>>>>> The reason its not quite that simple is that the input circuit on
> the
> >>>>>>> counter
> >>>>>>> really does not handle a 10 Hz audio tone as well as it handles a
> 10
> >>>> MHz
> >>>>>>> RF signal. Instead of getting 9 digits a second, you probably will
> >> get
> >>>>>>> three
> >>>>>>> *good* digits a second and another 6 digits of noise.
> >>>>>>>
> >>>>>>> The good news is that an op amp used as a preamp ( to get you up to
> >>>> maybe
> >>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as
> >>>>>>> limiters will
> >>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a
> high
> >>>> pass
> >>>>>>> and low pass filter ( DC offsets can be a problem ….) and you have
> a
> >>>>>>> working
> >>>>>>> device that gets into the parts in 10^-13 with your 5335.
> >>>>>>>
> >>>>>>> It all can be done with point to point wiring. No need for a PCB
> >>>> layout.
> >>>>>>> Be
> >>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and
> off
> >> at
> >>>>>>> the
> >>>>>>> same time ….
> >>>>>>>
> >>>>>>> Bob
> >>>>>>>
> >>>>>>
> >>>>> _______________________________________________
> >>>>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>>>> To unsubscribe, go to
> >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>>>> and follow the instructions there.
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>>> To unsubscribe, go to
> >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>>> and follow the instructions there.
> >>>>
> >>> _______________________________________________
> >>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>> and follow the instructions there.
> >>
> >>
> >> _______________________________________________
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >>
> >> _______________________________________________
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >>
> > _______________________________________________
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
BK
Bob kb8tq
Tue, Apr 14, 2020 12:26 PM
Hi
Indeed all a time tagger does is spit out picoseconds since some arbitrary
start point. Some run on and on forever ( counting up to pretty big numbers
in the process). Others roll over at a pre-defined point. You then massage
the data to take those out.
I’d suggest that the “software/ firmware included” and “fully debugged” nature
of the TAPR TICC make it pretty hard to beat unless you are planning to build a
couple dozen ….
Bob
On Apr 14, 2020, at 8:11 AM, Tobias Pluess tpluess@ieee.org wrote:
G'day
OK I see I must do it with time tagging :-)
Is it correct that the time tagging just spits out the time (in ns, for
example) when the rising edge on the A or B input occured? and then, you
calculate the phase by subtracting the time tags for the A channel from the
time tags for the B channel?
Riley also says that DMTD works better with time tagging, so I am not
surprised that you recommend it as well. However I hoped that some simple
measurements (only to get a ballpark figure) would be possible with my
current setup.
In fact, since I read the Riley paper about the DMTD system he built, I
have had my own design on my bucket list since quite a while. I planned to
make my own time-tag counter with two TDC7200 as interpolators, to get ps
resolution, very similar to the TAPR TICC.
Tobias
On Tue, Apr 14, 2020 at 1:48 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
If the phase slips are “well behaved” they can be handled. The problem
with a dual channel setup is that they are often not well behaved. The
period is 100 ns so a frequency drift of 1 ppb will put you in trouble in
under 2 minutes.
The only real answer is to do it properly and time tag the two outputs.
Any other approach will get you yelling and screaming at the test set.
Playing with two counters and not time tagging is in the “yelling and
screaming” category as well.
Get a TAPPR TICC if you really want to do a DMTD.
Of course you could just use a single mixer. That works fine with the
counter you already have. It will give you an A to B test just like a
DMTD. The only limitation is the need to tune at least one of the
oscillators
in each pair.
There is no requirement that you tune only one. If both are tunable,
you could tune one to the high end of its range and the other to the low
end.
With most OCXO’s, there is plenty of tune range.
Bob
On Apr 14, 2020, at 2:23 AM, Tobias Pluess tpluess@ieee.org wrote:
Hey Bob
ok now I see your point! you talk about the phase spillovers. Timelab and
also Stable32 can correct for them, so it shouldn't be a problem, right?
But I agree, if you cannot correct for the spillovers it becomes even
difficult.
Tobias
On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, kb8tq@n1k.org wrote:
Hi
The gotcha with using a conventional counter (as opposed to a time
is that you never know when things are going to “slip” past each other.
When they
do you get a major burp in your data. Bill’s setup is running a time
tagger ….
( = It runs an internal time count, each edge gets “labeled” with a
precise time
stamp that is good to nanoseconds or picoseconds. A Time Interval
simply measures the time between edges. That sounds like the same thing,
but
it’s not quite ….)
to compare two oscillators.
I don't know exactly how, though :-)
The gotcha with using a conventional counter (as opposed to a time
is that you never know when things are going to “slip” past each other.
When they
do you get a major burp in your data. Bill’s setup is running a time
tagger ….
OK and I see your point on the 8663. I will try to use another
I definitely didn't keep mine on for a long time. I didn't use the
generator for a while now, so it was unplugged for a few months. I
that's far from optimal for the 10811's stability.
Best approach is to mount your reference off on it’s own and just power
it. That way
you don’t wear out all the guts of a fancy piece of gear.
Bob
Tobias
On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, kb8tq@n1k.org wrote:
On Apr 13, 2020, at 5:06 PM, Tobias Pluess tpluess@ieee.org wrote:
Hi Bob
awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
Maybe I have some good OpAmps for this purpose in my box. I will try
of
You need something that is quiet (like the OP-37) and has a pretty
slew
rate. Past that, there are a lot of candidates. The TI OPA-228 family
course I saw that my setup was not ideal as there was a bit of noise
signals which I guess does lead to some jitter in the trigger circuit
therefore decreases my measurement noise floor.
Typically a good limiter takes you from 3 or 4 digits up to 6 or 7
digits.
Net result is a measurement that’s good in the vicinity of parts in
Can you say something about how it would be done using a TIC?
I don't have two identically good counters, but the HP 5335A could be
The standard way of doing the test is to run two counters / two TIC/s
two whatever’s.
I know of no practical way to do it with a single 5335.
And the offset source I used is not directly the HP 10811, but the HP
Signal generator internally uses a 10811 as reference source. But I
wait for days for it to warm up properly. (Should I?)
The 8663 synthesizer adds a lot of crud to the 10811. Regardless of
you
use the 10811, it needs to be on for a while. How long very much
on
just how long it’s been off. Best to keep it on all the time.
Yea, of course! :-)
I already implemented the ADEV, MDEV and TDEV calculations in Matlab
myself. I use TimeLab to see what numbers I should expect, and then I
to compute it all myself in Matlab because I want to see how it
Be careful any time you code this stuff for the first time. It’s
easy
( = I’ve done it ….) to make minor errors. That’s in no way to suggest
you should not code it up yourself. I generally do it in Excel or in
Best
Tobias
On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
Ok, first the math:
If your offset oscillator is 10 Hz high at 10 MHz, you have a:
10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
You get to add a 6 to what Time Lab shows you.
If you are getting an ADEV at 1 second of 1x10^-4 then that
gets you to 1x10^-10
So, what’s going on?
You can’t feed the mixer outputs straight into a counter. The
front
end does not handle LF audio sine waves very well. You need to do an
op-amp based limiter. A pair of OP-37’s in each leg ( or something
similar)
should do the trick.
Second, the offset source needs to be pretty good. A 10811 tuned
both the mechanical trim and the EFC is a pretty good choice to
If you only have one counter, simply ignore the second channel. You
running a single mixer. It still works as a comparison between the
oscillator
and your DUT.
If you want to do it properly as a DMTD, then you set up two
to measure mixer A and the other to measure mixer B. Set them both
measure frequency. Time tag the data files so you know which reading
matches up with which.
Fun !!!
Bob
Hi again Bob
I tried to do some measurements with a DMTD!
In my junk box I found a little PCB from earlier experiments on
with a power splitter and two SRA-3H mixers, it was even already
the DMTD configuration. So I gave it a try!
As "transfer oscillator" I used my HP 8663A signal generator, and
high in frequency by 10 Hz. To the two mixers, I connected the two
signals and at the mixer outputs, I put a little lowpass filter
corner frequency.
The output signals from the two SRA-3 mixers are almost 0.5Vpp, so
to feed them directly into the HP 5335A TIC and used the TI mode to
the delay between the two signals.
This gives 10 readings/sec, which I try to process with TimeLab.
It does give some interesting graphs, but I don't know yet how to
set up TimeLab for this kind of measurement. I.e. now, I get an
order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
simply need to multiply this with 1e-7 to get the real ADEV at
this would mean that my real ADEV is in the range of 1e-11 to
is indeed my target value, BUT I expect that things are not that
(i.e. what if I didn't set the transfer oscillator high by +10Hz
by 9.9Hz for example).
Can you give some hints on that?
Of course I also did the noise floor test (i.e. I fed the 10MHz
a power splitter and connected the two outputs to my DMTD with two
different lenghts of cables. This gave results starting at 1e-4
to 1e-7, maybe it would have gone even lower but I measured only
couple of minutes.)
Can you give some hints on that?
Best
Tobias
HB9FSX
On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
The quick way to do this is with a single mixer. Take something
old
10811 and use the coarse tune to set it high in frequency by 5 to
Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz
That tone is the difference between the 10811 and your device
test.
If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
If you measured the 10 MHz on the DUT, that 1 Hz would be a very
shift
( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
IF you could tack that on to the ADEV plot of your 5335 ( no,
that
simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
second.
The reason its not quite that simple is that the input circuit on
counter
really does not handle a 10 Hz audio tone as well as it handles a
RF signal. Instead of getting 9 digits a second, you probably
three
good digits a second and another 6 digits of noise.
The good news is that an op amp used as a preamp ( to get you up
32 V p-p rather than a volt or so) and another op amp or three as
limiters will
get you up around 6 or 7 good digits. Toss in a cap or two as a
and low pass filter ( DC offsets can be a problem ….) and you
working
device that gets into the parts in 10^-13 with your 5335.
It all can be done with point to point wiring. No need for a PCB
Be
careful that the +/- 18V supplies to the op amp both go on and
and follow the instructions there.
and follow the instructions there.
and follow the instructions there.
and follow the instructions there.
Hi
Indeed all a time tagger does is spit out picoseconds since some arbitrary
start point. Some run on and on forever ( counting up to pretty big numbers
in the process). Others roll over at a pre-defined point. You then massage
the data to take those out.
I’d suggest that the “software/ firmware included” and “fully debugged” nature
of the TAPR TICC make it pretty hard to beat unless you are planning to build a
couple dozen ….
Bob
> On Apr 14, 2020, at 8:11 AM, Tobias Pluess <tpluess@ieee.org> wrote:
>
> G'day
>
> OK I see I must do it with time tagging :-)
> Is it correct that the time tagging just spits out the time (in ns, for
> example) when the rising edge on the A or B input occured? and then, you
> calculate the phase by subtracting the time tags for the A channel from the
> time tags for the B channel?
> Riley also says that DMTD works better with time tagging, so I am not
> surprised that you recommend it as well. However I hoped that some simple
> measurements (only to get a ballpark figure) would be possible with my
> current setup.
> In fact, since I read the Riley paper about the DMTD system he built, I
> have had my own design on my bucket list since quite a while. I planned to
> make my own time-tag counter with two TDC7200 as interpolators, to get ps
> resolution, very similar to the TAPR TICC.
>
>
> Tobias
>
>
> On Tue, Apr 14, 2020 at 1:48 PM Bob kb8tq <kb8tq@n1k.org> wrote:
>
>> Hi
>>
>> If the phase slips are “well behaved” they can be handled. The problem
>> with a dual channel setup is that they are often not well behaved. The
>> period is 100 ns so a frequency drift of 1 ppb will put you in trouble in
>> under 2 minutes.
>>
>> The only real answer is to do it properly and time tag the two outputs.
>> Any other approach will get you yelling and screaming at the test set.
>> Playing with two counters and not time tagging is in the “yelling and
>> screaming” category as well.
>>
>> Get a TAPPR TICC if you really want to do a DMTD.
>>
>> Of course you *could* just use a single mixer. That works fine with the
>> counter you already have. It will give you an A to B test just like a
>> DMTD. The only limitation is the need to tune at least one of the
>> oscillators
>> in each pair.
>>
>> There is no requirement that you tune only one. If both are tunable,
>> you could tune one to the high end of its range and the other to the low
>> end.
>> With most OCXO’s, there is plenty of tune range.
>>
>> Bob
>>
>>> On Apr 14, 2020, at 2:23 AM, Tobias Pluess <tpluess@ieee.org> wrote:
>>>
>>> Hey Bob
>>>
>>> ok now I see your point! you talk about the phase spillovers. Timelab and
>>> also Stable32 can correct for them, so it shouldn't be a problem, right?
>>>
>>> But I agree, if you cannot correct for the spillovers it becomes even
>> more
>>> difficult.
>>>
>>>
>>> Tobias
>>>
>>> On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, <kb8tq@n1k.org> wrote:
>>>
>>>> Hi
>>>>
>>>> The gotcha with using a conventional counter (as opposed to a time
>> tagger)
>>>> is that you never know when things are going to “slip” past each other.
>>>> When they
>>>> do you get a major burp in your data. Bill’s setup is running a time
>>>> tagger ….
>>>>
>>>> ( = It runs an internal time count, each edge gets “labeled” with a
>>>> precise time
>>>> stamp that is good to nanoseconds or picoseconds. A Time Interval
>> Counter
>>>> simply measures the time between edges. That sounds like the same thing,
>>>> but
>>>> it’s not quite ….)
>>>>
>>>>
>>>>> On Apr 13, 2020, at 6:11 PM, Tobias Pluess <tpluess@ieee.org> wrote:
>>>>>
>>>>> Hi Bob
>>>>>
>>>>> Riley suggests to use a single TIC
>>>>>
>>>>> http://wriley.com/A%20Small%20DMTD%20System.pdf
>>>>>
>>>>> when you look at the block diagram Fig. 4, you can see that one TIC
>>>> allows
>>>>> to compare two oscillators.
>>>>> I don't know exactly how, though :-)
>>>>
>>>> The gotcha with using a conventional counter (as opposed to a time
>> tagger)
>>>> is that you never know when things are going to “slip” past each other.
>>>> When they
>>>> do you get a major burp in your data. Bill’s setup is running a time
>>>> tagger ….
>>>>
>>>>>
>>>>> OK and I see your point on the 8663. I will try to use another
>> reference!
>>>>> I definitely didn't keep mine on for a long time. I didn't use the
>> signal
>>>>> generator for a while now, so it was unplugged for a few months. I
>> assume
>>>>> that's far from optimal for the 10811's stability.
>>>>
>>>> Best approach is to mount your reference off on it’s own and just power
>>>> it. That way
>>>> you don’t wear out all the guts of a fancy piece of gear.
>>>>
>>>> Bob
>>>>
>>>>>
>>>>>
>>>>> Tobias
>>>>>
>>>>>
>>>>>
>>>>> On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote:
>>>>>
>>>>>> Hi
>>>>>>
>>>>>>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote:
>>>>>>>
>>>>>>> Hi Bob
>>>>>>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
>>>>>>>
>>>>>>> Maybe I have some good OpAmps for this purpose in my box. I will try
>>>> it!
>>>>>> of
>>>>>>
>>>>>> You need something that is quiet (like the OP-37) and has a pretty
>> good
>>>>>> slew
>>>>>> rate. Past that, there are a lot of candidates. The TI OPA-228 family
>> is
>>>>>> one.
>>>>>>
>>>>>>> course I saw that my setup was not ideal as there was a bit of noise
>> on
>>>>>> the
>>>>>>> signals which I guess does lead to some jitter in the trigger circuit
>>>> and
>>>>>>> therefore decreases my measurement noise floor.
>>>>>>
>>>>>> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7
>> good
>>>>>> digits.
>>>>>> Net result is a measurement that’s good in the vicinity of parts in
>>>> 10^-13
>>>>>>
>>>>>>>
>>>>>>> Can you say something about how it would be done using a TIC?
>>>>>>> I don't have two identically good counters, but the HP 5335A could be
>>>>>> used
>>>>>>> as TIC, couldn't it.
>>>>>>
>>>>>> The standard way of doing the test is to run two counters / two TIC/s
>> /
>>>>>> two whatever’s.
>>>>>> I know of no practical way to do it with a single 5335.
>>>>>>
>>>>>>>
>>>>>>> And the offset source I used is not directly the HP 10811, but the HP
>>>>>> 8663A
>>>>>>> Signal generator internally uses a 10811 as reference source. But I
>>>>>> didn't
>>>>>>> wait for days for it to warm up properly. (Should I?)
>>>>>>
>>>>>> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of
>>>> how
>>>>>> you
>>>>>> use the 10811, it needs to be on for a while. How long very much
>> depends
>>>>>> on
>>>>>> just how long it’s been off. Best to keep it on all the time.
>>>>>>
>>>>>>>
>>>>>>>> Fun !!!
>>>>>>> Yea, of course! :-)
>>>>>>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab
>> by
>>>>>>> myself. I use TimeLab to see what numbers I should expect, and then I
>>>>>> want
>>>>>>> to compute it all myself in Matlab because I want to see how it
>>>> actually
>>>>>>> works. ;-)
>>>>>>
>>>>>> Be careful any time you code this stuff for the first time. It’s
>>>> amazingly
>>>>>> easy
>>>>>> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest
>>>> that
>>>>>> you should not code it up yourself. I generally do it in Excel or in
>> C.
>>>>>>
>>>>>> Bob
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Best
>>>>>>> Tobias
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote:
>>>>>>>
>>>>>>>> Hi
>>>>>>>>
>>>>>>>> Ok, first the math:
>>>>>>>>
>>>>>>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
>>>>>>>>
>>>>>>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
>>>>>>>>
>>>>>>>> You get to add a 6 to what Time Lab shows you.
>>>>>>>>
>>>>>>>> If you are getting an ADEV at 1 second of 1x10^-4 then that
>> multiplier
>>>>>>>> gets you to 1x10^-10
>>>>>>>>
>>>>>>>> So, what’s going on?
>>>>>>>>
>>>>>>>> You can’t feed the mixer outputs straight into a counter. The
>> counter
>>>>>>>> front
>>>>>>>> end does not handle LF audio sine waves very well. You need to do an
>>>>>>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
>>>>>>>> similar)
>>>>>>>> should do the trick.
>>>>>>>>
>>>>>>>> Second, the offset source needs to be pretty good. A 10811 tuned
>> high
>>>>>> with
>>>>>>>> both the mechanical trim and the EFC is a pretty good choice to
>> start
>>>>>> out.
>>>>>>>>
>>>>>>>> If you only have one counter, simply ignore the second channel. You
>>>> are
>>>>>> now
>>>>>>>> running a single mixer. It still works as a comparison between the
>>>>>> offset
>>>>>>>> oscillator
>>>>>>>> and your DUT.
>>>>>>>>
>>>>>>>> If you want to do it properly as a DMTD, then you set up two
>> counters.
>>>>>> One
>>>>>>>> to measure mixer A and the other to measure mixer B. Set them both
>> up
>>>>>> to
>>>>>>>> measure frequency. Time tag the data files so you know which reading
>>>>>>>> matches up with which.
>>>>>>>>
>>>>>>>> Fun !!!
>>>>>>>>
>>>>>>>> Bob
>>>>>>>>
>>>>>>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org>
>> wrote:
>>>>>>>>>
>>>>>>>>> Hi again Bob
>>>>>>>>>
>>>>>>>>> I tried to do some measurements with a DMTD!
>>>>>>>>> In my junk box I found a little PCB from earlier experiments on
>> that
>>>>>>>> topic,
>>>>>>>>> with a power splitter and two SRA-3H mixers, it was even already
>>>> wired
>>>>>>>> for
>>>>>>>>> the DMTD configuration. So I gave it a try!
>>>>>>>>> As "transfer oscillator" I used my HP 8663A signal generator, and
>> set
>>>>>> it
>>>>>>>>> high in frequency by 10 Hz. To the two mixers, I connected the two
>>>>>> 10MHz
>>>>>>>>> signals and at the mixer outputs, I put a little lowpass filter
>> with
>>>>>>>> 100Hz
>>>>>>>>> corner frequency.
>>>>>>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so
>> I
>>>>>>>> tried
>>>>>>>>> to feed them directly into the HP 5335A TIC and used the TI mode to
>>>>>>>> measure
>>>>>>>>> the delay between the two signals.
>>>>>>>>> This gives 10 readings/sec, which I try to process with TimeLab.
>>>>>>>>> It does give some interesting graphs, but I don't know yet how to
>>>>>>>> correctly
>>>>>>>>> set up TimeLab for this kind of measurement. I.e. now, I get an
>> ADEV
>>>> in
>>>>>>>> the
>>>>>>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
>>>> mean
>>>>>> I
>>>>>>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at
>>>> 10MHz?
>>>>>>>>> this would mean that my real ADEV is in the range of 1e-11 to
>> 1e-12,
>>>>>>>> which
>>>>>>>>> is indeed my target value, BUT I expect that things are not that
>>>>>> simple.
>>>>>>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz
>> but
>>>>>> only
>>>>>>>>> by 9.9Hz for example).
>>>>>>>>> Can you give some hints on that?
>>>>>>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz
>>>> signal
>>>>>>>> into
>>>>>>>>> a power splitter and connected the two outputs to my DMTD with two
>>>>>>>>> different lenghts of cables. This gave results starting at 1e-4
>> going
>>>>>>>> down
>>>>>>>>> to 1e-7, maybe it would have gone even lower but I measured only
>> for
>>>> a
>>>>>>>>> couple of minutes.)
>>>>>>>>>
>>>>>>>>> Can you give some hints on that?
>>>>>>>>>
>>>>>>>>> Best
>>>>>>>>> Tobias
>>>>>>>>> HB9FSX
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote:
>>>>>>>>>>
>>>>>>>>>>> Hi
>>>>>>>>>>>
>>>>>>>>>>> The quick way to do this is with a single mixer. Take something
>>>> like
>>>>>> an
>>>>>>>>>>> old
>>>>>>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to
>>>> 10
>>>>>>>> Hz.
>>>>>>>>>>>
>>>>>>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz
>> audio
>>>>>>>> tone.
>>>>>>>>>>> That tone is the *difference* between the 10811 and your device
>>>> under
>>>>>>>>>>> test.
>>>>>>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
>>>>>>>>>>>
>>>>>>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very
>>>>>> small
>>>>>>>>>>> shift
>>>>>>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the
>>>>>>>> change
>>>>>>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
>>>>>> increase
>>>>>>>> ).
>>>>>>>>>>>
>>>>>>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no,
>>>> it’s
>>>>>>>> not
>>>>>>>>>>> that
>>>>>>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1
>>>>>>>>>>> second.
>>>>>>>>>>>
>>>>>>>>>>> The reason its not quite that simple is that the input circuit on
>>>> the
>>>>>>>>>>> counter
>>>>>>>>>>> really does not handle a 10 Hz audio tone as well as it handles a
>>>> 10
>>>>>>>> MHz
>>>>>>>>>>> RF signal. Instead of getting 9 digits a second, you probably
>> will
>>>>>> get
>>>>>>>>>>> three
>>>>>>>>>>> *good* digits a second and another 6 digits of noise.
>>>>>>>>>>>
>>>>>>>>>>> The good news is that an op amp used as a preamp ( to get you up
>> to
>>>>>>>> maybe
>>>>>>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as
>>>>>>>>>>> limiters will
>>>>>>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a
>>>> high
>>>>>>>> pass
>>>>>>>>>>> and low pass filter ( DC offsets can be a problem ….) and you
>> have
>>>> a
>>>>>>>>>>> working
>>>>>>>>>>> device that gets into the parts in 10^-13 with your 5335.
>>>>>>>>>>>
>>>>>>>>>>> It all can be done with point to point wiring. No need for a PCB
>>>>>>>> layout.
>>>>>>>>>>> Be
>>>>>>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and
>>>> off
>>>>>> at
>>>>>>>>>>> the
>>>>>>>>>>> same time ….
>>>>>>>>>>>
>>>>>>>>>>> Bob
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>>>>>>>> To unsubscribe, go to
>>>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>>>>>>> and follow the instructions there.
>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>>>>>>> To unsubscribe, go to
>>>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>>>>>> and follow the instructions there.
>>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>>>>>> To unsubscribe, go to
>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>>>>> and follow the instructions there.
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>>>>> To unsubscribe, go to
>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>>>> and follow the instructions there.
>>>>>>
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
>>>>> To unsubscribe, go to
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>>>>> and follow the instructions there.
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>>>>
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TP
Tobias Pluess
Tue, Apr 14, 2020 12:35 PM
Hi
yes sure I agree that it is hard to beat. But from a
commercial perspective, any hobby is more or less nonsense - the same is
true for my own GPSDO. I just could have bought one and would be finished.
But making my own is more interesting ;-) I'll see whether I buy a TAPR
TICC. Maybe it would come in handy to have something I can compare with.
Tobias
On Tue., 14 Apr. 2020, 14:27 Bob kb8tq, kb8tq@n1k.org wrote:
Hi
Indeed all a time tagger does is spit out picoseconds since some arbitrary
start point. Some run on and on forever ( counting up to pretty big numbers
in the process). Others roll over at a pre-defined point. You then massage
the data to take those out.
I’d suggest that the “software/ firmware included” and “fully debugged”
nature
of the TAPR TICC make it pretty hard to beat unless you are planning to
build a
couple dozen ….
Bob
On Apr 14, 2020, at 8:11 AM, Tobias Pluess tpluess@ieee.org wrote:
G'day
OK I see I must do it with time tagging :-)
Is it correct that the time tagging just spits out the time (in ns, for
example) when the rising edge on the A or B input occured? and then, you
calculate the phase by subtracting the time tags for the A channel from
time tags for the B channel?
Riley also says that DMTD works better with time tagging, so I am not
surprised that you recommend it as well. However I hoped that some simple
measurements (only to get a ballpark figure) would be possible with my
current setup.
In fact, since I read the Riley paper about the DMTD system he built, I
have had my own design on my bucket list since quite a while. I planned
make my own time-tag counter with two TDC7200 as interpolators, to get ps
resolution, very similar to the TAPR TICC.
Tobias
On Tue, Apr 14, 2020 at 1:48 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
If the phase slips are “well behaved” they can be handled. The problem
with a dual channel setup is that they are often not well behaved. The
period is 100 ns so a frequency drift of 1 ppb will put you in trouble
under 2 minutes.
The only real answer is to do it properly and time tag the two outputs.
Any other approach will get you yelling and screaming at the test set.
Playing with two counters and not time tagging is in the “yelling and
screaming” category as well.
Get a TAPPR TICC if you really want to do a DMTD.
Of course you could just use a single mixer. That works fine with the
counter you already have. It will give you an A to B test just like a
DMTD. The only limitation is the need to tune at least one of the
oscillators
in each pair.
There is no requirement that you tune only one. If both are tunable,
you could tune one to the high end of its range and the other to the low
end.
With most OCXO’s, there is plenty of tune range.
Bob
On Apr 14, 2020, at 2:23 AM, Tobias Pluess tpluess@ieee.org wrote:
Hey Bob
ok now I see your point! you talk about the phase spillovers. Timelab
also Stable32 can correct for them, so it shouldn't be a problem,
But I agree, if you cannot correct for the spillovers it becomes even
difficult.
Tobias
On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, kb8tq@n1k.org wrote:
Hi
The gotcha with using a conventional counter (as opposed to a time
is that you never know when things are going to “slip” past each
When they
do you get a major burp in your data. Bill’s setup is running a time
tagger ….
( = It runs an internal time count, each edge gets “labeled” with a
precise time
stamp that is good to nanoseconds or picoseconds. A Time Interval
simply measures the time between edges. That sounds like the same
to compare two oscillators.
I don't know exactly how, though :-)
The gotcha with using a conventional counter (as opposed to a time
is that you never know when things are going to “slip” past each
When they
do you get a major burp in your data. Bill’s setup is running a time
tagger ….
OK and I see your point on the 8663. I will try to use another
I definitely didn't keep mine on for a long time. I didn't use the
generator for a while now, so it was unplugged for a few months. I
that's far from optimal for the 10811's stability.
Best approach is to mount your reference off on it’s own and just
it. That way
you don’t wear out all the guts of a fancy piece of gear.
Bob
Tobias
On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, kb8tq@n1k.org wrote:
Hi Bob
awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
Maybe I have some good OpAmps for this purpose in my box. I will
of
You need something that is quiet (like the OP-37) and has a pretty
slew
rate. Past that, there are a lot of candidates. The TI OPA-228
course I saw that my setup was not ideal as there was a bit of
signals which I guess does lead to some jitter in the trigger
therefore decreases my measurement noise floor.
Typically a good limiter takes you from 3 or 4 digits up to 6 or 7
digits.
Net result is a measurement that’s good in the vicinity of parts in
Can you say something about how it would be done using a TIC?
I don't have two identically good counters, but the HP 5335A could
The standard way of doing the test is to run two counters / two
two whatever’s.
I know of no practical way to do it with a single 5335.
And the offset source I used is not directly the HP 10811, but the
Signal generator internally uses a 10811 as reference source. But I
wait for days for it to warm up properly. (Should I?)
The 8663 synthesizer adds a lot of crud to the 10811. Regardless
you
use the 10811, it needs to be on for a while. How long very much
on
just how long it’s been off. Best to keep it on all the time.
Yea, of course! :-)
I already implemented the ADEV, MDEV and TDEV calculations in
myself. I use TimeLab to see what numbers I should expect, and
to compute it all myself in Matlab because I want to see how it
Be careful any time you code this stuff for the first time. It’s
easy
( = I’ve done it ….) to make minor errors. That’s in no way to
you should not code it up yourself. I generally do it in Excel or in
Best
Tobias
On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
Ok, first the math:
If your offset oscillator is 10 Hz high at 10 MHz, you have a:
10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
You get to add a 6 to what Time Lab shows you.
If you are getting an ADEV at 1 second of 1x10^-4 then that
gets you to 1x10^-10
So, what’s going on?
You can’t feed the mixer outputs straight into a counter. The
front
end does not handle LF audio sine waves very well. You need to do
op-amp based limiter. A pair of OP-37’s in each leg ( or something
similar)
should do the trick.
Second, the offset source needs to be pretty good. A 10811 tuned
both the mechanical trim and the EFC is a pretty good choice to
If you only have one counter, simply ignore the second channel.
running a single mixer. It still works as a comparison between the
oscillator
and your DUT.
If you want to do it properly as a DMTD, then you set up two
to measure mixer A and the other to measure mixer B. Set them
measure frequency. Time tag the data files so you know which
matches up with which.
Fun !!!
Bob
Hi again Bob
I tried to do some measurements with a DMTD!
In my junk box I found a little PCB from earlier experiments on
with a power splitter and two SRA-3H mixers, it was even already
the DMTD configuration. So I gave it a try!
As "transfer oscillator" I used my HP 8663A signal generator, and
high in frequency by 10 Hz. To the two mixers, I connected the
signals and at the mixer outputs, I put a little lowpass filter
corner frequency.
The output signals from the two SRA-3 mixers are almost 0.5Vpp,
to feed them directly into the HP 5335A TIC and used the TI mode
the delay between the two signals.
This gives 10 readings/sec, which I try to process with TimeLab.
It does give some interesting graphs, but I don't know yet how to
set up TimeLab for this kind of measurement. I.e. now, I get an
order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
simply need to multiply this with 1e-7 to get the real ADEV at
this would mean that my real ADEV is in the range of 1e-11 to
is indeed my target value, BUT I expect that things are not that
(i.e. what if I didn't set the transfer oscillator high by +10Hz
by 9.9Hz for example).
Can you give some hints on that?
Of course I also did the noise floor test (i.e. I fed the 10MHz
a power splitter and connected the two outputs to my DMTD with
different lenghts of cables. This gave results starting at 1e-4
to 1e-7, maybe it would have gone even lower but I measured only
couple of minutes.)
Can you give some hints on that?
Best
Tobias
HB9FSX
On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
The quick way to do this is with a single mixer. Take something
old
10811 and use the coarse tune to set it high in frequency by 5
Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz
That tone is the difference between the 10811 and your device
test.
If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
If you measured the 10 MHz on the DUT, that 1 Hz would be a
shift
( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified”
in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
IF you could tack that on to the ADEV plot of your 5335 ( no,
that
simple) your 7x10^-10 at 1 second would become more 7x10^-16
second.
The reason its not quite that simple is that the input circuit
counter
really does not handle a 10 Hz audio tone as well as it
RF signal. Instead of getting 9 digits a second, you probably
three
good digits a second and another 6 digits of noise.
The good news is that an op amp used as a preamp ( to get you
32 V p-p rather than a volt or so) and another op amp or three
limiters will
get you up around 6 or 7 good digits. Toss in a cap or two as a
and low pass filter ( DC offsets can be a problem ….) and you
working
device that gets into the parts in 10^-13 with your 5335.
It all can be done with point to point wiring. No need for a
Be
careful that the +/- 18V supplies to the op amp both go on
and follow the instructions there.
and follow the instructions there.
and follow the instructions there.
and follow the instructions there.
and follow the instructions there.
Hi
yes sure I agree that it is hard to beat. But from a
commercial perspective, any hobby is more or less nonsense - the same is
true for my own GPSDO. I just could have bought one and would be finished.
But making my own is more interesting ;-) I'll see whether I buy a TAPR
TICC. Maybe it would come in handy to have something I can compare with.
Tobias
On Tue., 14 Apr. 2020, 14:27 Bob kb8tq, <kb8tq@n1k.org> wrote:
> Hi
>
> Indeed all a time tagger does is spit out picoseconds since some arbitrary
> start point. Some run on and on forever ( counting up to pretty big numbers
> in the process). Others roll over at a pre-defined point. You then massage
> the data to take those out.
>
> I’d suggest that the “software/ firmware included” and “fully debugged”
> nature
> of the TAPR TICC make it pretty hard to beat unless you are planning to
> build a
> couple dozen ….
>
>
> Bob
>
> > On Apr 14, 2020, at 8:11 AM, Tobias Pluess <tpluess@ieee.org> wrote:
> >
> > G'day
> >
> > OK I see I must do it with time tagging :-)
> > Is it correct that the time tagging just spits out the time (in ns, for
> > example) when the rising edge on the A or B input occured? and then, you
> > calculate the phase by subtracting the time tags for the A channel from
> the
> > time tags for the B channel?
> > Riley also says that DMTD works better with time tagging, so I am not
> > surprised that you recommend it as well. However I hoped that some simple
> > measurements (only to get a ballpark figure) would be possible with my
> > current setup.
> > In fact, since I read the Riley paper about the DMTD system he built, I
> > have had my own design on my bucket list since quite a while. I planned
> to
> > make my own time-tag counter with two TDC7200 as interpolators, to get ps
> > resolution, very similar to the TAPR TICC.
> >
> >
> > Tobias
> >
> >
> > On Tue, Apr 14, 2020 at 1:48 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >
> >> Hi
> >>
> >> If the phase slips are “well behaved” they can be handled. The problem
> >> with a dual channel setup is that they are often not well behaved. The
> >> period is 100 ns so a frequency drift of 1 ppb will put you in trouble
> in
> >> under 2 minutes.
> >>
> >> The only real answer is to do it properly and time tag the two outputs.
> >> Any other approach will get you yelling and screaming at the test set.
> >> Playing with two counters and not time tagging is in the “yelling and
> >> screaming” category as well.
> >>
> >> Get a TAPPR TICC if you really want to do a DMTD.
> >>
> >> Of course you *could* just use a single mixer. That works fine with the
> >> counter you already have. It will give you an A to B test just like a
> >> DMTD. The only limitation is the need to tune at least one of the
> >> oscillators
> >> in each pair.
> >>
> >> There is no requirement that you tune only one. If both are tunable,
> >> you could tune one to the high end of its range and the other to the low
> >> end.
> >> With most OCXO’s, there is plenty of tune range.
> >>
> >> Bob
> >>
> >>> On Apr 14, 2020, at 2:23 AM, Tobias Pluess <tpluess@ieee.org> wrote:
> >>>
> >>> Hey Bob
> >>>
> >>> ok now I see your point! you talk about the phase spillovers. Timelab
> and
> >>> also Stable32 can correct for them, so it shouldn't be a problem,
> right?
> >>>
> >>> But I agree, if you cannot correct for the spillovers it becomes even
> >> more
> >>> difficult.
> >>>
> >>>
> >>> Tobias
> >>>
> >>> On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, <kb8tq@n1k.org> wrote:
> >>>
> >>>> Hi
> >>>>
> >>>> The gotcha with using a conventional counter (as opposed to a time
> >> tagger)
> >>>> is that you never know when things are going to “slip” past each
> other.
> >>>> When they
> >>>> do you get a major burp in your data. Bill’s setup is running a time
> >>>> tagger ….
> >>>>
> >>>> ( = It runs an internal time count, each edge gets “labeled” with a
> >>>> precise time
> >>>> stamp that is good to nanoseconds or picoseconds. A Time Interval
> >> Counter
> >>>> simply measures the time between edges. That sounds like the same
> thing,
> >>>> but
> >>>> it’s not quite ….)
> >>>>
> >>>>
> >>>>> On Apr 13, 2020, at 6:11 PM, Tobias Pluess <tpluess@ieee.org> wrote:
> >>>>>
> >>>>> Hi Bob
> >>>>>
> >>>>> Riley suggests to use a single TIC
> >>>>>
> >>>>> http://wriley.com/A%20Small%20DMTD%20System.pdf
> >>>>>
> >>>>> when you look at the block diagram Fig. 4, you can see that one TIC
> >>>> allows
> >>>>> to compare two oscillators.
> >>>>> I don't know exactly how, though :-)
> >>>>
> >>>> The gotcha with using a conventional counter (as opposed to a time
> >> tagger)
> >>>> is that you never know when things are going to “slip” past each
> other.
> >>>> When they
> >>>> do you get a major burp in your data. Bill’s setup is running a time
> >>>> tagger ….
> >>>>
> >>>>>
> >>>>> OK and I see your point on the 8663. I will try to use another
> >> reference!
> >>>>> I definitely didn't keep mine on for a long time. I didn't use the
> >> signal
> >>>>> generator for a while now, so it was unplugged for a few months. I
> >> assume
> >>>>> that's far from optimal for the 10811's stability.
> >>>>
> >>>> Best approach is to mount your reference off on it’s own and just
> power
> >>>> it. That way
> >>>> you don’t wear out all the guts of a fancy piece of gear.
> >>>>
> >>>> Bob
> >>>>
> >>>>>
> >>>>>
> >>>>> Tobias
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote:
> >>>>>
> >>>>>> Hi
> >>>>>>
> >>>>>>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org>
> wrote:
> >>>>>>>
> >>>>>>> Hi Bob
> >>>>>>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-)
> >>>>>>>
> >>>>>>> Maybe I have some good OpAmps for this purpose in my box. I will
> try
> >>>> it!
> >>>>>> of
> >>>>>>
> >>>>>> You need something that is quiet (like the OP-37) and has a pretty
> >> good
> >>>>>> slew
> >>>>>> rate. Past that, there are a lot of candidates. The TI OPA-228
> family
> >> is
> >>>>>> one.
> >>>>>>
> >>>>>>> course I saw that my setup was not ideal as there was a bit of
> noise
> >> on
> >>>>>> the
> >>>>>>> signals which I guess does lead to some jitter in the trigger
> circuit
> >>>> and
> >>>>>>> therefore decreases my measurement noise floor.
> >>>>>>
> >>>>>> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7
> >> good
> >>>>>> digits.
> >>>>>> Net result is a measurement that’s good in the vicinity of parts in
> >>>> 10^-13
> >>>>>>
> >>>>>>>
> >>>>>>> Can you say something about how it would be done using a TIC?
> >>>>>>> I don't have two identically good counters, but the HP 5335A could
> be
> >>>>>> used
> >>>>>>> as TIC, couldn't it.
> >>>>>>
> >>>>>> The standard way of doing the test is to run two counters / two
> TIC/s
> >> /
> >>>>>> two whatever’s.
> >>>>>> I know of no practical way to do it with a single 5335.
> >>>>>>
> >>>>>>>
> >>>>>>> And the offset source I used is not directly the HP 10811, but the
> HP
> >>>>>> 8663A
> >>>>>>> Signal generator internally uses a 10811 as reference source. But I
> >>>>>> didn't
> >>>>>>> wait for days for it to warm up properly. (Should I?)
> >>>>>>
> >>>>>> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless
> of
> >>>> how
> >>>>>> you
> >>>>>> use the 10811, it needs to be on for a while. How long very much
> >> depends
> >>>>>> on
> >>>>>> just how long it’s been off. Best to keep it on all the time.
> >>>>>>
> >>>>>>>
> >>>>>>>> Fun !!!
> >>>>>>> Yea, of course! :-)
> >>>>>>> I already implemented the ADEV, MDEV and TDEV calculations in
> Matlab
> >> by
> >>>>>>> myself. I use TimeLab to see what numbers I should expect, and
> then I
> >>>>>> want
> >>>>>>> to compute it all myself in Matlab because I want to see how it
> >>>> actually
> >>>>>>> works. ;-)
> >>>>>>
> >>>>>> Be careful any time you code this stuff for the first time. It’s
> >>>> amazingly
> >>>>>> easy
> >>>>>> ( = I’ve done it ….) to make minor errors. That’s in no way to
> suggest
> >>>> that
> >>>>>> you should not code it up yourself. I generally do it in Excel or in
> >> C.
> >>>>>>
> >>>>>> Bob
> >>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> Best
> >>>>>>> Tobias
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >>>>>>>
> >>>>>>>> Hi
> >>>>>>>>
> >>>>>>>> Ok, first the math:
> >>>>>>>>
> >>>>>>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a:
> >>>>>>>>
> >>>>>>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD
> >>>>>>>>
> >>>>>>>> You get to add a 6 to what Time Lab shows you.
> >>>>>>>>
> >>>>>>>> If you are getting an ADEV at 1 second of 1x10^-4 then that
> >> multiplier
> >>>>>>>> gets you to 1x10^-10
> >>>>>>>>
> >>>>>>>> So, what’s going on?
> >>>>>>>>
> >>>>>>>> You can’t feed the mixer outputs straight into a counter. The
> >> counter
> >>>>>>>> front
> >>>>>>>> end does not handle LF audio sine waves very well. You need to do
> an
> >>>>>>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something
> >>>>>>>> similar)
> >>>>>>>> should do the trick.
> >>>>>>>>
> >>>>>>>> Second, the offset source needs to be pretty good. A 10811 tuned
> >> high
> >>>>>> with
> >>>>>>>> both the mechanical trim and the EFC is a pretty good choice to
> >> start
> >>>>>> out.
> >>>>>>>>
> >>>>>>>> If you only have one counter, simply ignore the second channel.
> You
> >>>> are
> >>>>>> now
> >>>>>>>> running a single mixer. It still works as a comparison between the
> >>>>>> offset
> >>>>>>>> oscillator
> >>>>>>>> and your DUT.
> >>>>>>>>
> >>>>>>>> If you want to do it properly as a DMTD, then you set up two
> >> counters.
> >>>>>> One
> >>>>>>>> to measure mixer A and the other to measure mixer B. Set them
> both
> >> up
> >>>>>> to
> >>>>>>>> measure frequency. Time tag the data files so you know which
> reading
> >>>>>>>> matches up with which.
> >>>>>>>>
> >>>>>>>> Fun !!!
> >>>>>>>>
> >>>>>>>> Bob
> >>>>>>>>
> >>>>>>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org>
> >> wrote:
> >>>>>>>>>
> >>>>>>>>> Hi again Bob
> >>>>>>>>>
> >>>>>>>>> I tried to do some measurements with a DMTD!
> >>>>>>>>> In my junk box I found a little PCB from earlier experiments on
> >> that
> >>>>>>>> topic,
> >>>>>>>>> with a power splitter and two SRA-3H mixers, it was even already
> >>>> wired
> >>>>>>>> for
> >>>>>>>>> the DMTD configuration. So I gave it a try!
> >>>>>>>>> As "transfer oscillator" I used my HP 8663A signal generator, and
> >> set
> >>>>>> it
> >>>>>>>>> high in frequency by 10 Hz. To the two mixers, I connected the
> two
> >>>>>> 10MHz
> >>>>>>>>> signals and at the mixer outputs, I put a little lowpass filter
> >> with
> >>>>>>>> 100Hz
> >>>>>>>>> corner frequency.
> >>>>>>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp,
> so
> >> I
> >>>>>>>> tried
> >>>>>>>>> to feed them directly into the HP 5335A TIC and used the TI mode
> to
> >>>>>>>> measure
> >>>>>>>>> the delay between the two signals.
> >>>>>>>>> This gives 10 readings/sec, which I try to process with TimeLab.
> >>>>>>>>> It does give some interesting graphs, but I don't know yet how to
> >>>>>>>> correctly
> >>>>>>>>> set up TimeLab for this kind of measurement. I.e. now, I get an
> >> ADEV
> >>>> in
> >>>>>>>> the
> >>>>>>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that
> >>>> mean
> >>>>>> I
> >>>>>>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at
> >>>> 10MHz?
> >>>>>>>>> this would mean that my real ADEV is in the range of 1e-11 to
> >> 1e-12,
> >>>>>>>> which
> >>>>>>>>> is indeed my target value, BUT I expect that things are not that
> >>>>>> simple.
> >>>>>>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz
> >> but
> >>>>>> only
> >>>>>>>>> by 9.9Hz for example).
> >>>>>>>>> Can you give some hints on that?
> >>>>>>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz
> >>>> signal
> >>>>>>>> into
> >>>>>>>>> a power splitter and connected the two outputs to my DMTD with
> two
> >>>>>>>>> different lenghts of cables. This gave results starting at 1e-4
> >> going
> >>>>>>>> down
> >>>>>>>>> to 1e-7, maybe it would have gone even lower but I measured only
> >> for
> >>>> a
> >>>>>>>>> couple of minutes.)
> >>>>>>>>>
> >>>>>>>>> Can you give some hints on that?
> >>>>>>>>>
> >>>>>>>>> Best
> >>>>>>>>> Tobias
> >>>>>>>>> HB9FSX
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >>>>>>>>>>
> >>>>>>>>>>> Hi
> >>>>>>>>>>>
> >>>>>>>>>>> The quick way to do this is with a single mixer. Take something
> >>>> like
> >>>>>> an
> >>>>>>>>>>> old
> >>>>>>>>>>> 10811 and use the coarse tune to set it high in frequency by 5
> to
> >>>> 10
> >>>>>>>> Hz.
> >>>>>>>>>>>
> >>>>>>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz
> >> audio
> >>>>>>>> tone.
> >>>>>>>>>>> That tone is the *difference* between the 10811 and your device
> >>>> under
> >>>>>>>>>>> test.
> >>>>>>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz.
> >>>>>>>>>>>
> >>>>>>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a
> very
> >>>>>> small
> >>>>>>>>>>> shift
> >>>>>>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified”
> the
> >>>>>>>> change
> >>>>>>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X
> >>>>>> increase
> >>>>>>>> ).
> >>>>>>>>>>>
> >>>>>>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no,
> >>>> it’s
> >>>>>>>> not
> >>>>>>>>>>> that
> >>>>>>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16
> at 1
> >>>>>>>>>>> second.
> >>>>>>>>>>>
> >>>>>>>>>>> The reason its not quite that simple is that the input circuit
> on
> >>>> the
> >>>>>>>>>>> counter
> >>>>>>>>>>> really does not handle a 10 Hz audio tone as well as it
> handles a
> >>>> 10
> >>>>>>>> MHz
> >>>>>>>>>>> RF signal. Instead of getting 9 digits a second, you probably
> >> will
> >>>>>> get
> >>>>>>>>>>> three
> >>>>>>>>>>> *good* digits a second and another 6 digits of noise.
> >>>>>>>>>>>
> >>>>>>>>>>> The good news is that an op amp used as a preamp ( to get you
> up
> >> to
> >>>>>>>> maybe
> >>>>>>>>>>> 32 V p-p rather than a volt or so) and another op amp or three
> as
> >>>>>>>>>>> limiters will
> >>>>>>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a
> >>>> high
> >>>>>>>> pass
> >>>>>>>>>>> and low pass filter ( DC offsets can be a problem ….) and you
> >> have
> >>>> a
> >>>>>>>>>>> working
> >>>>>>>>>>> device that gets into the parts in 10^-13 with your 5335.
> >>>>>>>>>>>
> >>>>>>>>>>> It all can be done with point to point wiring. No need for a
> PCB
> >>>>>>>> layout.
> >>>>>>>>>>> Be
> >>>>>>>>>>> careful that the +/- 18V supplies to the op amp *both* go on
> and
> >>>> off
> >>>>>> at
> >>>>>>>>>>> the
> >>>>>>>>>>> same time ….
> >>>>>>>>>>>
> >>>>>>>>>>> Bob
> >>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>> _______________________________________________
> >>>>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>>>>>>>> To unsubscribe, go to
> >>>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>>>>>>>> and follow the instructions there.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> _______________________________________________
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> >>>>>>>> To unsubscribe, go to
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> >>>>>>>> and follow the instructions there.
> >>>>>>>>
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> >>>>>>> To unsubscribe, go to
> >>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>>>>>> and follow the instructions there.
> >>>>>>
> >>>>>>
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> >>>>>> To unsubscribe, go to
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> >>
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> > and follow the instructions there.
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> _______________________________________________
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> and follow the instructions there.
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BK
Bob kb8tq
Tue, Apr 14, 2020 12:50 PM
Hi
The whole “volume of clutter” on the desk / bench / around the lab / basement
is one of the many drivers getting me to move over to some of the more
modern USB based measurement gear. You can swap out 400 lb of cranky
(but useful ) gear from the 1960’s for what would fit in a small backpack.
Even at work, the same sort of drivers applied. A USB based box was something
that you could have a dozen of out on many benches. The big beast setup hulked
away on it’s own bench over in the corner. A lot more got done with the little boxes.
There are a lot of grades of USB gear. I’m not suggesting that my $100 network
analyzer competes for accuracy with a shiny new R&S or Keysight device. It just
might do as good a job as the broken down pile of gear from 1968 though. For
a bit more than $100, I could get a better USB version ….
=====
Can you build your own TICC / scope / network analyzer / PC / television?
Sure you can. It’s just parts put together in this or that fashion. Getting one to the
point that it measures up with what you can buy will take a while (likely a couple
of passes).
Your time is “free" since this is a hobby. Does that really include 40 hours a week
for a year to get this or that pass done? At least to me … nope. How about the lab
full of application specific test gear to get this piece of gear debugged before you
can use it ? Hmmm….
Simply getting the board laid out is the easy part of any of this. On a normal
product design, the work to get to that point is maybe 10% of the effort put in
to get the job done. A home project may be even more lopsided since it likely
is the first time you have done this or that.
Lots of twists and turns. Lots of projects started and never fully completed.
I have piles and piles of them ….
Bob
On Apr 14, 2020, at 8:15 AM, Tobias Pluess tpluess@ieee.org wrote:
Hi Bob
yes sure I know. At least my homebrew GPSDO and the STAR4 GPSDO I have are
always powered, but since they don't take much space on my desk that's
okay. But for the signal generators (or SpecAn etc) it is a completely
different story; I usually take them from the shelf when I need them and
put them back afterwards, because they simply take too much space away. And
my home lab has only limited space, unfortunately. I am thinking since
months about a better setup (how arrange everything, how to stack my
equipment and such) but it is not so easy because simply stacking all
equipment on top of each other is unsatisfactory (in that case one needs in
general the instrument at the very top, which is simply too far away :-)).
The 8663A is a nice machine, but it would fill my desk already by 50%, so
no way to leave it there (and therefore I cannot keep it powered).
Tobias
On Tue, Apr 14, 2020 at 1:54 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
The whole “volume of clutter” on the desk / bench / around the lab / basement
is one of the many drivers getting me to move over to some of the more
modern USB based measurement gear. You can swap out 400 lb of cranky
(but useful ) gear from the 1960’s for what would fit in a small backpack.
Even at work, the same sort of drivers applied. A USB based box was something
that you could have a dozen of out on many benches. The big beast setup hulked
away on it’s own bench over in the corner. A lot more got done with the little boxes.
There are a lot of grades of USB gear. I’m not suggesting that my $100 network
analyzer competes for accuracy with a shiny new R&S or Keysight device. It just
*might* do as good a job as the broken down pile of gear from 1968 though. For
a bit more than $100, I could get a better USB version ….
=====
Can you build your own TICC / scope / network analyzer / PC / television?
Sure you can. It’s just parts put together in this or that fashion. Getting one to the
point that it measures up with what you can buy will take a while (likely a couple
of passes).
Your time is “free" since this is a hobby. Does that really include 40 hours a week
for a year to get this or that pass done? At least to me … nope. How about the lab
full of application specific test gear to get this piece of gear debugged *before* you
can use it ? Hmmm….
Simply getting the board laid out is the easy part of any of this. On a normal
product design, the work to get to that point is maybe 10% of the effort put in
to get the job done. A home project may be even more lopsided since it likely
is the first time you have done this or that.
Lots of twists and turns. Lots of projects started and never fully completed.
I have piles and piles of them ….
Bob
> On Apr 14, 2020, at 8:15 AM, Tobias Pluess <tpluess@ieee.org> wrote:
>
> Hi Bob
> yes sure I know. At least my homebrew GPSDO and the STAR4 GPSDO I have are
> always powered, but since they don't take much space on my desk that's
> okay. But for the signal generators (or SpecAn etc) it is a completely
> different story; I usually take them from the shelf when I need them and
> put them back afterwards, because they simply take too much space away. And
> my home lab has only limited space, unfortunately. I am thinking since
> months about a better setup (how arrange everything, how to stack my
> equipment and such) but it is not so easy because simply stacking all
> equipment on top of each other is unsatisfactory (in that case one needs in
> general the instrument at the very top, which is simply too far away :-)).
> The 8663A is a nice machine, but it would fill my desk already by 50%, so
> no way to leave it there (and therefore I cannot keep it powered).
>
> Tobias
>
>
> On Tue, Apr 14, 2020 at 1:54 PM Bob kb8tq <kb8tq@n1k.org> wrote:
>
>> Hi
>>
>>> On Apr 14, 2020, at 2:31 AM, Tobias Pluess <tpluess@ieee.org> wrote:
>>>
TP
Tobias Pluess
Tue, Apr 14, 2020 3:01 PM
Hi Bob
yes I totally agree, you can save a lot of space by having those USB boxes
for almost every measurement.
However I am happy that we have at work the "old school stuff" (by which I
don't mean we have old equipment, actually it is pretty modern) because in
my opinion the user experience is much better if you have buttons to press
and knobs to rotate. I don't like the scopes where you have to set up
everything via touchscreen, and I don't like the USB scopes. Therefore I am
actually quite happy with the kind of equipment that sits in its own box,
the disadvantage is that it needs space. However I think this is only a
concern for the homelab, where space is limited. A place where they don't
have the space to install a proper network analyzer is perhaps a bit ...
funny, I'd say. But for home usage you're probably right. However many of
the USB things have lots of drawbacks the "pro" equipment doesn't have. But
perhaps we are wandering off the subject a bit now :-)
Lots of projects started and never fully completed. I have piles and
piles of them ….
yeah I know. I have them as well. Not piles, but certainly quite a few. But
I have also piles of stuff I have finished. For instance from time to time
I try to manufacture RF waveguide components like directional couplers and
bandpass filters and the like. While I don't actually need them I simply
want to see whether I could make them and how precise it is possible. (it
is possible quite accurately up to perhaps 80GHz, above that precision
becomes an issue). And as you know especially the waveguide stuff is bulky
:-) I even once made my own N connectors just to see whether it was
possible. (it is, as well. When gold plated or at least polished, they look
very similar to the commercial ones.)
But this is definitely seriously off-topic ;-) To ask a back-to-topic
question: you said you wrote your own programs to extract ADEV from
timetagged data. Could you give a hint on how you "massage" (as you said)
the data from the time tagger to get proper phase info and ADEV?
Tobias
On Tue, Apr 14, 2020 at 2:51 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
The whole “volume of clutter” on the desk / bench / around the lab /
basement
is one of the many drivers getting me to move over to some of the more
modern USB based measurement gear. You can swap out 400 lb of cranky
(but useful ) gear from the 1960’s for what would fit in a small
backpack.
Even at work, the same sort of drivers applied. A USB based box was
something
that you could have a dozen of out on many benches. The big beast setup
hulked
away on it’s own bench over in the corner. A lot more got done with the
little boxes.
There are a lot of grades of USB gear. I’m not suggesting that my $100
network
analyzer competes for accuracy with a shiny new R&S or Keysight device. It
just
might do as good a job as the broken down pile of gear from 1968 though.
For
a bit more than $100, I could get a better USB version ….
=====
Can you build your own TICC / scope / network analyzer / PC / television?
Sure you can. It’s just parts put together in this or that fashion.
Getting one to the
point that it measures up with what you can buy will take a while (likely
a couple
of passes).
Your time is “free" since this is a hobby. Does that really include 40
hours a week
for a year to get this or that pass done? At least to me … nope. How about
the lab
full of application specific test gear to get this piece of gear debugged
before you
can use it ? Hmmm….
Simply getting the board laid out is the easy part of any of this. On a
normal
product design, the work to get to that point is maybe 10% of the effort
put in
to get the job done. A home project may be even more lopsided since it
likely
is the first time you have done this or that.
Lots of twists and turns. Lots of projects started and never fully
completed.
I have piles and piles of them ….
Bob
On Apr 14, 2020, at 8:15 AM, Tobias Pluess tpluess@ieee.org wrote:
Hi Bob
yes sure I know. At least my homebrew GPSDO and the STAR4 GPSDO I have
always powered, but since they don't take much space on my desk that's
okay. But for the signal generators (or SpecAn etc) it is a completely
different story; I usually take them from the shelf when I need them and
put them back afterwards, because they simply take too much space away.
my home lab has only limited space, unfortunately. I am thinking since
months about a better setup (how arrange everything, how to stack my
equipment and such) but it is not so easy because simply stacking all
equipment on top of each other is unsatisfactory (in that case one needs
general the instrument at the very top, which is simply too far away
The 8663A is a nice machine, but it would fill my desk already by 50%, so
no way to leave it there (and therefore I cannot keep it powered).
Tobias
On Tue, Apr 14, 2020 at 1:54 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi Bob
yes I totally agree, you can save a lot of space by having those USB boxes
for almost every measurement.
However I am happy that we have at work the "old school stuff" (by which I
don't mean we have old equipment, actually it is pretty modern) because in
my opinion the user experience is much better if you have buttons to press
and knobs to rotate. I don't like the scopes where you have to set up
everything via touchscreen, and I don't like the USB scopes. Therefore I am
actually quite happy with the kind of equipment that sits in its own box,
the disadvantage is that it needs space. However I think this is only a
concern for the homelab, where space is limited. A place where they don't
have the space to install a proper network analyzer is perhaps a bit ...
funny, I'd say. But for home usage you're probably right. However many of
the USB things have lots of drawbacks the "pro" equipment doesn't have. But
perhaps we are wandering off the subject a bit now :-)
> Lots of projects started and never fully completed. I have piles and
piles of them ….
yeah I know. I have them as well. Not piles, but certainly quite a few. But
I have also piles of stuff I have finished. For instance from time to time
I try to manufacture RF waveguide components like directional couplers and
bandpass filters and the like. While I don't actually need them I simply
want to see whether I could make them and how precise it is possible. (it
is possible quite accurately up to perhaps 80GHz, above that precision
becomes an issue). And as you know especially the waveguide stuff is bulky
:-) I even once made my own N connectors just to see whether it was
possible. (it is, as well. When gold plated or at least polished, they look
very similar to the commercial ones.)
But this is definitely seriously off-topic ;-) To ask a back-to-topic
question: you said you wrote your own programs to extract ADEV from
timetagged data. Could you give a hint on how you "massage" (as you said)
the data from the time tagger to get proper phase info and ADEV?
Tobias
On Tue, Apr 14, 2020 at 2:51 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> Hi
>
> The whole “volume of clutter” on the desk / bench / around the lab /
> basement
> is one of the many drivers getting me to move over to some of the more
> modern USB based measurement gear. You can swap out 400 lb of cranky
> (but useful ) gear from the 1960’s for what would fit in a small
> backpack.
>
> Even at work, the same sort of drivers applied. A USB based box was
> something
> that you could have a dozen of out on many benches. The big beast setup
> hulked
> away on it’s own bench over in the corner. A lot more got done with the
> little boxes.
>
> There are a lot of grades of USB gear. I’m not suggesting that my $100
> network
> analyzer competes for accuracy with a shiny new R&S or Keysight device. It
> just
> *might* do as good a job as the broken down pile of gear from 1968 though.
> For
> a bit more than $100, I could get a better USB version ….
>
> =====
>
> Can you build your own TICC / scope / network analyzer / PC / television?
> Sure you can. It’s just parts put together in this or that fashion.
> Getting one to the
> point that it measures up with what you can buy will take a while (likely
> a couple
> of passes).
>
> Your time is “free" since this is a hobby. Does that really include 40
> hours a week
> for a year to get this or that pass done? At least to me … nope. How about
> the lab
> full of application specific test gear to get this piece of gear debugged
> *before* you
> can use it ? Hmmm….
>
> Simply getting the board laid out is the easy part of any of this. On a
> normal
> product design, the work to get to that point is maybe 10% of the effort
> put in
> to get the job done. A home project may be even more lopsided since it
> likely
> is the first time you have done this or that.
>
> Lots of twists and turns. Lots of projects started and never fully
> completed.
> I have piles and piles of them ….
>
> Bob
>
> > On Apr 14, 2020, at 8:15 AM, Tobias Pluess <tpluess@ieee.org> wrote:
> >
> > Hi Bob
> > yes sure I know. At least my homebrew GPSDO and the STAR4 GPSDO I have
> are
> > always powered, but since they don't take much space on my desk that's
> > okay. But for the signal generators (or SpecAn etc) it is a completely
> > different story; I usually take them from the shelf when I need them and
> > put them back afterwards, because they simply take too much space away.
> And
> > my home lab has only limited space, unfortunately. I am thinking since
> > months about a better setup (how arrange everything, how to stack my
> > equipment and such) but it is not so easy because simply stacking all
> > equipment on top of each other is unsatisfactory (in that case one needs
> in
> > general the instrument at the very top, which is simply too far away
> :-)).
> > The 8663A is a nice machine, but it would fill my desk already by 50%, so
> > no way to leave it there (and therefore I cannot keep it powered).
> >
> > Tobias
> >
> >
> > On Tue, Apr 14, 2020 at 1:54 PM Bob kb8tq <kb8tq@n1k.org> wrote:
> >
> >> Hi
> >>
> >>> On Apr 14, 2020, at 2:31 AM, Tobias Pluess <tpluess@ieee.org> wrote:
> >>>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
