Symmetricom/Datum FTS-1050A Disciplined Frequency Standard
I happen to have a 11729C carrier noise test set sitting on the shelf
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-----Original Message-----
From: Pluess, Tobias via time-nuts [mailto:time-nuts@lists.febo.com]
Sent: Monday, August 15, 2022 3:58 AM
To: Discussion of precise time and frequency measurement
Cc: Pluess, Tobias
Subject: [time-nuts] Re: Phase noise of HP8663A 640 MHz reference?
Hi Ed,
could you share some info about your own 640 MHz source?
I would be very interested.
I do have an 8663A, but I have no idea about how good it actually is and
currently, I don't have a possibility to test it because I still lack an
11729C carrier noise test set (but I would like to make something similar
myself some day). Apparently my 8663A is one of the latest units, because
it is already labelled Agilent.
best
Tobias
On Sun, Aug 14, 2022 at 8:11 PM ed breya via time-nuts <
time-nuts@lists.febo.com> wrote:
Thanks all, for replies and possibly running some tests. The reason I'm
asking about this is that now that I finally have the HP8663A, I'd like
to rig it up with the HP11179C, and its documentation mentions all this
option 3 stuff on the 8663A. So I started wondering, just how good is
it, and if there's a "typical" or representative spec. Again, I believe
option 3 just means that the particular unit was tested at the factory
before delivery, and the results documented and included with the unit.
Over time, this info could be lost.
My unit has option 2 only, which is fancier phase modulation, that could
be handy for some things. Before it arrived, I studied up the design and
evolution in the manuals. It appears that the 8662A and earlier 8663A
models may have had the 10544 OCXO installed, while mine is one of the
later versions, officially sporting the 10811-60111. I found that this
is indeed what's in there, and the cal seal is marked ca 2014 - likely
the last time it was messed with. It seems to work so far, and it is
quite an impressive beast.
On the 11179C, I had a stroll down memory lane for a while. I kind of
forgot how much I had worked on it about a dozen years ago. Since I had
no prospect of getting a 8662A or 8663A back then, I had been collecting
and mounting parts to make a fairly high grade built-in 640 MHz source.
The scheme was based on a 80 MHz VTOCXO, to be doubled up and filtered
thrice to 640 MHz, and phase locked to 10 MHz if needed. I already had
all the major pieces fitted, and a bunch of notes on the design details.
I started yanking all this stuff out to restore it to stock, but then
started thinking "not so fast - maybe this could be pretty good after
all." Since I really don't know how good the 640 MHz from the 8663A is,
I'll keep all the pieces and info from the other scheme together, just
in case.
Ed
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Thank you John Miles for putting together the great summary of 8663A
comparisons and spec info. That pretty much tells the story. I think the
bottom line is that any 8663A will be fairly close (within 10 dB) to the
option 3 description, but no guarantee.
Ed
Tobias wrote
"Hi Ed, could you share some info about your own 640 MHz source?
I would be very interested.
I do have an 8663A, but I have no idea about how good it actually is and
currently, I don't have a possibility to test it because I still lack an
11729C carrier noise test set (but I would like to make something
similar myself some day)."
The plan was to do the doubling and amplifying similar to the
8662A/8663A (which I think are about the same in this respect), except
that I don't have anything like the mentioned 40 MHz and 160 MHz crystal
filters. Starting from the higher OCXO frequency should help some,
depending on its noise performance.
The filters I do have can't fix anything close-in, but should work very
well on spurious content from almost any multiplier scheme. The first
one especially is a single unit 160 MHz BPF made from two tubular
coaxial ones cascaded. I didn't make it - it came this way as a
commercial product. It has enormous stop-band suppression maybe 200 dB
(theoretical) by +/- 10 MHz away from fc, but large insertion loss about
10 dB. The plan was to double the 80 MHz OCXO into this filter, which
should eradicate all spurious from below. The 320 and 640 MHz BPFs are
more conventional.
The 80 MHz OCXO was apparently quite common around 20-30 years ago.
Despite this, I couldn't find any specs twelve years ago, and can't find
any today, even though there seems to be plenty of them still around and
for sale. The ones I have are Vectron 229-9237, and 229-5657-1,
apparently the same except for mechanical construction.
I have a bunch of similar units, mostly oddball frequencies in the 100
MHz range, and I did have to take some apart (soldered shut cans) over
the years to modify for particular projects. I found they all used
half-frequency crystals and built in doublers. The 80 MHz is no
exception - a quick look on the SA shows it's a 40 MHz OCXO that's
doubled up internally, so it's really only starting with a four times
frequency versus multiplying a 10 MHz reference.
Another thing I noticed is that the 640 MHz SAW BPF in the 11729C may
not be for closer in spurious content, but mostly wide cleanup, and
optimized to form a good oscillator when used for that mode. The manual
says that the purpose of the filter is to reduce 120 MHz, 520 MHz, and
760 MHz spurs. These and others naturally come from the rather
complicated 8662A/8663A reference generator/multiplier system, and the
640 MHz output does not appear to have very much isolation from all this
activity.
So, if you make your own 640 MHz "clean and simple" by direct
multiplication, with no side deals for other frequencies, the result
will not include the extra stuff that would be coming from the
generator. If you also start with a good HF OCXO with known specs, and
do careful multiplication, filtering, and PLLing, I think it can beat
the noise performance of the 8662A/8663A's 640 MHz source. How much? I
dunno, but suspect that the hump from around 10 Hz to 10 kHz may be due
in part to all the reference making and synthesizing action going on in
there, that's somehow included in the 640 MHz output. That is, presuming
the 10 MHz internal reference has no such hump. If it does, then it
could be simply the result of the multiplication factor, and unavoidable.
Ed
If you start at 100 MHz, there is a good 400 MHz SAW filter
<
https://www.digikey.de/de/products/detail/qualcomm-rf-front-end-rffe-filters/B39401B3742H110/1858962?s=N4IgTCBcDaIEYGYDsAWCBdAvkA
for spurious cleanup at $2 per pop. With 250 KHz BW it cannot do much
against close-in phase noise but 2 of them back-to-back deliver
quite clean a carrier at 400 MHz. Even if you just dump a 100 MHz 5V
LVCMOS signal into it. (2*74LVC1G125 etc buffers).
That delivers abt. -6 dBm @400.
Picture: R7, R8 can be smaller, MMIC can be SKY65014 with less gain.
Tested with an ECOC2522 100 MHz oven whose PN plots I passed on here
some months ago.
Mr. Fourier nags that *4 is not so fortunate with a ~ 1:1 hi/low
source,
but there is enough left. Diode doublers with their 10 dB loss each
are also not the bee's knees.
<
https://www.digikey.de/de/products/detail/ecs-inc/ECOC-2522-100-000-5HS/6579018
That's a nice clock source for a LMX2594 15 GHz synthesizer
in integer mode or for a DDS, or for a 432-> 32 MHz down converter for
SDR.
The filters may be driven with 10 dBm and feature abt. 2 dB loss.
There are also GPS filters at 1600 MHz that include 4*400 MHz.
I saw "usable BW = 2 MHz" on the DS cover page, but the VNA revealed
more like 35 MHz. The data sheets of both Qualcom an Taiyu Yuden
are quite a mess.
Nevertheless these filters are an option for multiplier chains.
Soldering them is not for the faint of heart with 5 pads on 1 mm**2.
The 400 MHz filter is harmless in this respect.
Using them in a box that also contains GPS is probably not
a lucky design.
I wished there was sth. for 300 MHz (LMX2594 in fractional mode)
Cheers, Gerhard
Am 2022-08-21 23:52, schrieb ed breya via time-nuts:
....
On 8/21/2022 8:19 PM, Gerhard Hoffmann via time-nuts wrote:
If you start at 100 MHz, there is a good 400 MHz SAW filter
<
https://www.digikey.de/de/products/detail/qualcomm-rf-front-end-rffe-filters/B39401B3742H110/1858962?s=N4IgTCBcDaIEYGYDsAWCBdAvkA
>
for spurious cleanup at $2 per pop. With 250 KHz BW it cannot do much
against close-in phase noise but 2 of them back-to-back deliver
quite clean a carrier at 400 MHz. Even if you just dump a 100 MHz 5V
Actually, if can have a big effect on close in phase noise. Meaning
it can make it a lot worse, due to the filter's intrinsic flicker noise.
Especially at the $2 price point.
Rick
Here are some PN plots from the PN9000.(mixer version, not the xcor version)
The upper plots are the 8663's v. the PN9000 synthesizer. The lower
plot is the two 8663's, one is the VCO and the other is the DUT. PN
data of the lower plot is attached. I've got 2 more 8663s I can
measure, once my hernia belt is back from the cleaners.
Jim
On 2022-08-21 5:52 PM, ed breya via time-nuts wrote:
Tobias wrote
"Hi Ed, could you share some info about your own 640 MHz source?
I would be very interested.
I do have an 8663A, but I have no idea about how good it actually is and
currently, I don't have a possibility to test it because I still lack an
11729C carrier noise test set (but I would like to make something
similar myself some day)."
The plan was to do the doubling and amplifying similar to the
8662A/8663A (which I think are about the same in this respect), except
that I don't have anything like the mentioned 40 MHz and 160 MHz
crystal filters. Starting from the higher OCXO frequency should help
some, depending on its noise performance.
The filters I do have can't fix anything close-in, but should work
very well on spurious content from almost any multiplier scheme. The
first one especially is a single unit 160 MHz BPF made from two
tubular coaxial ones cascaded. I didn't make it - it came this way as
a commercial product. It has enormous stop-band suppression maybe 200
dB (theoretical) by +/- 10 MHz away from fc, but large insertion loss
about 10 dB. The plan was to double the 80 MHz OCXO into this filter,
which should eradicate all spurious from below. The 320 and 640 MHz
BPFs are more conventional.
The 80 MHz OCXO was apparently quite common around 20-30 years ago.
Despite this, I couldn't find any specs twelve years ago, and can't
find any today, even though there seems to be plenty of them still
around and for sale. The ones I have are Vectron 229-9237, and
229-5657-1, apparently the same except for mechanical construction.
I have a bunch of similar units, mostly oddball frequencies in the 100
MHz range, and I did have to take some apart (soldered shut cans) over
the years to modify for particular projects. I found they all used
half-frequency crystals and built in doublers. The 80 MHz is no
exception - a quick look on the SA shows it's a 40 MHz OCXO that's
doubled up internally, so it's really only starting with a four times
frequency versus multiplying a 10 MHz reference.
Another thing I noticed is that the 640 MHz SAW BPF in the 11729C may
not be for closer in spurious content, but mostly wide cleanup, and
optimized to form a good oscillator when used for that mode. The
manual says that the purpose of the filter is to reduce 120 MHz, 520
MHz, and 760 MHz spurs. These and others naturally come from the
rather complicated 8662A/8663A reference generator/multiplier system,
and the 640 MHz output does not appear to have very much isolation
from all this activity.
So, if you make your own 640 MHz "clean and simple" by direct
multiplication, with no side deals for other frequencies, the result
will not include the extra stuff that would be coming from the
generator. If you also start with a good HF OCXO with known specs, and
do careful multiplication, filtering, and PLLing, I think it can beat
the noise performance of the 8662A/8663A's 640 MHz source. How much? I
dunno, but suspect that the hump from around 10 Hz to 10 kHz may be
due in part to all the reference making and synthesizing action going
on in there, that's somehow included in the 640 MHz output. That is,
presuming the 10 MHz internal reference has no such hump. If it does,
then it could be simply the result of the multiplication factor, and
unavoidable.
Ed
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--
Jim Muehlberg
Senior Engineer
National Radio Astronomy Observatory
ngVLA Local Oscillator Lead
1180 Boxwood Estates Rd B-111
Charlottesville, VA 22903-4602
P 434.296.0270
C 434.422.2017
Sorry for not including the plot. I guess the list won't accept inline
images.
I did not include data from the PN9000 synthesizer referenced plots,
because of course, you're not interested in the synthesizer noise, which
dominated.
Jim
On 8/22/2022 2:45 PM, Jim Muehlberg via time-nuts wrote:
Here are some PN plots from the PN9000.(mixer version, not the xcor
version)
The upper plots are the 8663's v. the PN9000 synthesizer. The lower
plot is the two 8663's, one is the VCO and the other is the DUT. PN
data of the lower plot is attached. I've got 2 more 8663s I can
measure, once my hernia belt is back from the cleaners.
Jim
On 2022-08-21 5:52 PM, ed breya via time-nuts wrote:
Tobias wrote
"Hi Ed, could you share some info about your own 640 MHz source?
I would be very interested.
I do have an 8663A, but I have no idea about how good it actually is and
currently, I don't have a possibility to test it because I still lack an
11729C carrier noise test set (but I would like to make something
similar myself some day)."
The plan was to do the doubling and amplifying similar to the
8662A/8663A (which I think are about the same in this respect),
except that I don't have anything like the mentioned 40 MHz and 160
MHz crystal filters. Starting from the higher OCXO frequency should
help some, depending on its noise performance.
The filters I do have can't fix anything close-in, but should work
very well on spurious content from almost any multiplier scheme. The
first one especially is a single unit 160 MHz BPF made from two
tubular coaxial ones cascaded. I didn't make it - it came this way as
a commercial product. It has enormous stop-band suppression maybe 200
dB (theoretical) by +/- 10 MHz away from fc, but large insertion loss
about 10 dB. The plan was to double the 80 MHz OCXO into this filter,
which should eradicate all spurious from below. The 320 and 640 MHz
BPFs are more conventional.
The 80 MHz OCXO was apparently quite common around 20-30 years ago.
Despite this, I couldn't find any specs twelve years ago, and can't
find any today, even though there seems to be plenty of them still
around and for sale. The ones I have are Vectron 229-9237, and
229-5657-1, apparently the same except for mechanical construction.
I have a bunch of similar units, mostly oddball frequencies in the
100 MHz range, and I did have to take some apart (soldered shut cans)
over the years to modify for particular projects. I found they all
used half-frequency crystals and built in doublers. The 80 MHz is no
exception - a quick look on the SA shows it's a 40 MHz OCXO that's
doubled up internally, so it's really only starting with a four times
frequency versus multiplying a 10 MHz reference.
Another thing I noticed is that the 640 MHz SAW BPF in the 11729C may
not be for closer in spurious content, but mostly wide cleanup, and
optimized to form a good oscillator when used for that mode. The
manual says that the purpose of the filter is to reduce 120 MHz, 520
MHz, and 760 MHz spurs. These and others naturally come from the
rather complicated 8662A/8663A reference generator/multiplier system,
and the 640 MHz output does not appear to have very much isolation
from all this activity.
So, if you make your own 640 MHz "clean and simple" by direct
multiplication, with no side deals for other frequencies, the result
will not include the extra stuff that would be coming from the
generator. If you also start with a good HF OCXO with known specs,
and do careful multiplication, filtering, and PLLing, I think it can
beat the noise performance of the 8662A/8663A's 640 MHz source. How
much? I dunno, but suspect that the hump from around 10 Hz to 10 kHz
may be due in part to all the reference making and synthesizing
action going on in there, that's somehow included in the 640 MHz
output. That is, presuming the 10 MHz internal reference has no such
hump. If it does, then it could be simply the result of the
multiplication factor, and unavoidable.
Ed
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--
Jim Muehlberg
Senior Engineer
National Radio Astronomy Observatory
ngVLA Local Oscillator Lead
1180 Boxwood Estates Rd B-111
Charlottesville, VA 22903-4602
P 434.296.0270
F 434.296.0324
www.cv.nrao.edu/~jmuehlbe
Going through some parts inventory and sorting exercise, I have a bunch
of these MLP-102 mixers, salvaged from a bunch of nearly identical RF
modules long ago. The environment was around 1 GHz RF and LO or a little
more, and 70 MHz IF. They are in the common 8-pin relay can style like
MCL SRA-1.
I believe that I found some meager data on them many years ago, but
trying recently, nothing whatsoever. Does anyone happen to have such
info, like from an old (1980s) KDI RF parts catalog? Some are marked
EMCO, and some KDI/EMCO.
Ed
Maybe EMCO (sales agent in Germany) can help you.
Here are the contact data:
EMCO Elektronik GmbH
Fraunhoferstrasse 14
D-82152 Planegg/Germany
Tel +49 (0)89 895 5650
Fax +49 (0)89 895 56510
info@emco-elektronik.de
Best regards
Bernd
-----Ursprüngliche Nachricht-----
Von: ed breya via time-nuts [mailto:time-nuts@lists.febo.com]
Gesendet: Donnerstag, 25. August 2022 07:29
An: time-nuts@lists.febo.com
Cc: ed breya eb@telight.com
Betreff: [time-nuts] Looking for info on KDI/EMCO MLP-102 DBM
Going through some parts inventory and sorting exercise, I have a bunch of
these MLP-102 mixers, salvaged from a bunch of nearly identical RF modules
long ago. The environment was around 1 GHz RF and LO or a little more, and
70 MHz IF. They are in the common 8-pin relay can style like MCL SRA-1.
I believe that I found some meager data on them many years ago, but trying
recently, nothing whatsoever. Does anyone happen to have such info, like
from an old (1980s) KDI RF parts catalog? Some are marked EMCO, and some
KDI/EMCO.
Ed
time-nuts mailing list -- time-nuts@lists.febo.com
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Since it appears there's no nice and easy way to access the OCXO coarse
tuning cap (there almost certainly is one in there, whether it's
accessible or not), a practical fix is a simple circuit mod (add one
resistor) to the DAC circuit.
I looked up the AD1861, and see that it has the typical built in opamp
and feedback resistor for current to voltage conversion. Also,
apparently, depending on hookup and the data formatting, it can be
arranged to go between +/- 3V output. The simplest way to fix the output
range issue, without changing the basic hookup, any software, or VCO
gain factors, is to just add pure DC offset current at the summing node.
If you need the output voltage to be more plus, then pull some current
from the summing node into the -5V supply through a resistor. The FS
current from the DAC seems to be around 1-2 mA, so a value for R in the
few to tens of k-ohms range can move it significantly. Just figure out
what the scaling actually is, and set it up for enough offset to keep
the range good for a while - you can adjust again as it ages. Two things
that will be different from original is that the external offset R won't
track the internal feedback R thermally, and using the minus 5V for a
reference may not be as clean as you'd want. The data sheet I found
doesn't say much about the internal reference, but I'm guessing it's a
+1.25 or 2.5V bandgap. Or, it may simply be the +5V supply.
Since it's overall in a closed loop feedback system, the offset R
tracking is probably irrelevant, but the noise on the -5V may be an
issue, depending on the PLL characteristics. First prove the concept
with what you already have, then refine it as needed.
Good luck.
Ed