Programmable clock for BFO use....noise
Off topic for this list, but you guys are experts in oscillator noise!
Playing with some mechanical filters. Need USB and LSB crystals for the BFO. No one seems to make crystals anymore, especially in the 253 KHz range!
Looking at the DigiKey Cardinal programmable oscillators. Cheap and available: CPPC1LZ A5B6
Anyone have an idea how noisy these would be after a division by 4 to get them in range?
Thanks,
N0UU
Not sure it would be the noise divided by 4. Not a useful answer.
I looked at those types of units. I thought they were factory programmed.
I may be wrong but was not of the opinion they were single unit buys.
Regards
WB8TSL
On Fri, Sep 14, 2018 at 12:14 PM, lstoskopf@cox.net wrote:
Off topic for this list, but you guys are experts in oscillator noise!
Playing with some mechanical filters. Need USB and LSB crystals for the
BFO. No one seems to make crystals anymore, especially in the 253 KHz
range!
Looking at the DigiKey Cardinal programmable oscillators. Cheap and
available: CPPC1LZ A5B6
Anyone have an idea how noisy these would be after a division by 4 to get
them in range?
Thanks,
N0UU
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and follow the instructions there.
I'd look for the appropriate crystals. If it will help, I have a 250.00 kHz one
you can have.
Wes N7WS
On 9/14/2018 9:14 AM, lstoskopf@cox.net wrote:
Off topic for this list, but you guys are experts in oscillator noise!
Playing with some mechanical filters. Need USB and LSB crystals for the BFO. No one seems to make crystals anymore, especially in the 253 KHz range!
Looking at the DigiKey Cardinal programmable oscillators. Cheap and available: CPPC1LZ A5B6
Anyone have an idea how noisy these would be after a division by 4 to get them in range?
Thanks,
N0UU
time-nuts mailing list -- time-nuts@lists.febo.com
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and follow the instructions there.
Frequency dividers can be pretty low noise, if you choose the right class
of logic. I remember that
at one time in the distant past, LSTTL was considered king. Unfortunately
I've been out of touch
with frequency dividers long enough to be ignorant of what works well today.
i'd suggest trying something with either HC-series or AC-series CMOS,
chances are fair that you'd
be happy. Write me off list and I'll tell you which well-known distributor
still has an excellent
selection of HC and AC parts in stock.
Dana
On Fri, Sep 14, 2018 at 11:14 AM, lstoskopf@cox.net wrote:
Off topic for this list, but you guys are experts in oscillator noise!
Playing with some mechanical filters. Need USB and LSB crystals for the
BFO. No one seems to make crystals anymore, especially in the 253 KHz
range!
Looking at the DigiKey Cardinal programmable oscillators. Cheap and
available: CPPC1LZ A5B6
Anyone have an idea how noisy these would be after a division by 4 to get
them in range?
Thanks,
N0UU
time-nuts mailing list -- time-nuts@lists.febo.com
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listinfo/time-nuts_lists.febo.com
and follow the instructions there.
I encountered these oscillators on a circuit I inherited
from another engineer. The spectrum of these is quite
dirty and they should only be considered as digital clock
oscillators. An additional annoyance is that they are
not marked with the frequency they are programmed to,
so if you have USB and LSB you'll have to put a dot
of paint on them or something to tell them apart.
Dividing by 4 or N will reduce spurs by 20 LOG N as
any time nut knows. If you get a programmable oscillator
at a frequency around 32 MHz and divide it down by 128
to ~253 kHz, you might get enough clean up for your
purposes. 20 LOG 128 = 42 dB.
Alternately, find a conventional clock
oscillator that can be divided by an even integer to hit
your BFO frequency. For example, 20 MHz divided by
78 = 256.4 kHz. 20 MHz divided by 80 = 250 kHz.
Divide by 39 followed by divide by 2 or divide by 40
followed by divide by 2, in order to get a square wave
at the output.
Rick N6RK
On 9/14/2018 9:14 AM, lstoskopf@cox.net wrote:
Off topic for this list, but you guys are experts in oscillator noise!
Playing with some mechanical filters. Need USB and LSB crystals for the BFO. No one seems to make crystals anymore, especially in the 253 KHz range!
Looking at the DigiKey Cardinal programmable oscillators. Cheap and available: CPPC1LZ A5B6
Anyone have an idea how noisy these would be after a division by 4 to get them in range?
Thanks,
N0UU
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.
The AC series is really quite good on phase noise; I used it in
the 5071A at 80 MHz.
Rick N6RK
On 9/14/2018 12:55 PM, Dana Whitlow wrote:
Frequency dividers can be pretty low noise, if you choose the right class
of logic. I remember that
at one time in the distant past, LSTTL was considered king. Unfortunately
I've been out of touch
with frequency dividers long enough to be ignorant of what works well today.
i'd suggest trying something with either HC-series or AC-series CMOS,
As a suggestion I collaborate with a Canadian ham some 5 years ago using a
DDS as a BFO for the HP 3586. Those details were shared on time-nuts if
they are still in the archives.That worked really well. I recall he was a
VE3??? The 3586 had 2 crystals for the BFO while the entire rest of the
system was locked to a single reference. Adding the DDS really reduced the
BFO behaviors that we typical hams wouldn't really notice. It also sound
very clean.
Regards
Paul
WB8TSL
On Fri, Sep 14, 2018 at 4:26 PM, Richard (Rick) Karlquist <
richard@karlquist.com> wrote:
The AC series is really quite good on phase noise; I used it in
the 5071A at 80 MHz.
Rick N6RK
On 9/14/2018 12:55 PM, Dana Whitlow wrote:
Frequency dividers can be pretty low noise, if you choose the right class
of logic. I remember that
at one time in the distant past, LSTTL was considered king. Unfortunately
I've been out of touch
with frequency dividers long enough to be ignorant of what works well
today.
i'd suggest trying something with either HC-series or AC-series CMOS,
time-nuts mailing list -- time-nuts@lists.febo.com
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listinfo/time-nuts_lists.febo.com
and follow the instructions there.
I would be interested in hearing more of the more suitable classes of logic chips. I have a 20Mhz rubidium that I wanted to divide down to 10Mhz
-=Bryan=-
From: time-nuts time-nuts-bounces@lists.febo.com on behalf of Dana Whitlow k8yumdoober@gmail.com
Sent: September 14, 2018 12:55 PM
To: lstoskopf@cox.net; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Programmable clock for BFO use....noise
Frequency dividers can be pretty low noise, if you choose the right class
of logic. I remember that
at one time in the distant past, LSTTL was considered king. Unfortunately
I've been out of touch
with frequency dividers long enough to be ignorant of what works well today.
i'd suggest trying something with either HC-series or AC-series CMOS,
chances are fair that you'd
be happy. Write me off list and I'll tell you which well-known distributor
still has an excellent
selection of HC and AC parts in stock.
Dana
On Fri, Sep 14, 2018 at 11:14 AM, lstoskopf@cox.net wrote:
Off topic for this list, but you guys are experts in oscillator noise!
Playing with some mechanical filters. Need USB and LSB crystals for the
BFO. No one seems to make crystals anymore, especially in the 253 KHz
range!
Looking at the DigiKey Cardinal programmable oscillators. Cheap and
available: CPPC1LZ A5B6
Anyone have an idea how noisy these would be after a division by 4 to get
them in range?
Thanks,
N0UU
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.
Those programmable oscillators look interesting. I went to Cardinal the
website to learn more, but they're pretty sparse on details. It looks
like they make all sorts of crystals, OC, TC, and VT XO modules, etc,
and these programmable ones, which are apparently PLL-based oscillators
locked to an XO. They don't say much more, but if you asked, maybe
they'd give some usable info.
There was also some mention of their own shortcomings with phase noise
and jitter, circa 2005, and how the later generations are much improved.
I'd say that since the programmed frequency is at least XO-based, then
its stability seems to be specified and can be good, but the noise etc
of the associated PLL inside does not seem to specified. It may be OK
for the application to just pick a certain frequency that would be
easier on the PLL (if you knew more about it and the XO frequency they
would use), and easy to divide down to your end results. I would wonder
what the few-off cost would be for the appropriate base parts and
programming.
They also seem to have custom crystal building service, which could be
very handy, depending on the cost. I've often needed oddball frequencies
for various projects, and wished it was easy and cheap to just order
some up.
Another trick you can try, that I've resorted to a number of times, is
to find two "standard" or common (or oddball ones that you happen to
already have) crystal frequencies that you can mix to get the desired
result. The combinations of various crystals and possible dividing
ratios may yield something close enough to tweak in. An EXCEL sheet can
help organize the info and choices.
Finally, of course, you can use DDS. This is nearly an ideal case for
this, since you want to make stuff around 250 kHz, but necessarily must
(for lack of in-range XOs) use a clock in the MHz region - maybe ten to
a hundred times higher than the output, so easy to get a good sine out.
Between the various XO clock frequencies available, and the program
choices in the DDS, it should be possible to come up with a nice scheme
to make whatever you want down in that range.
Ed
Finally, of course, you can use DDS. This is nearly an ideal case for
The trouble with a DDS is that you need a microcontroller with
software just to baby sit the thing.
Rick N6RK