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General => Buy/Sell/Wanted => Topic started by: testpoint1 on November 15, 2019, 12:02:53 am

Title: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: testpoint1 on November 15, 2019, 12:02:53 am
by gps disciplined (more than 24 hours result, less than 24 hours the value will NOT been stored to EEPROM);

price is 750 USD, https://www.ebay.com/itm/184036643084 (https://www.ebay.com/itm/184036643084)

if you found a complete atomic clock's price is less than 1K USD and the accuracy can reach mine, just tell me.

Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: testpoint1 on November 24, 2019, 06:54:50 am
if you need the Spectratime made, just check here:

https://www.ebay.com/itm/184050224670 (https://www.ebay.com/itm/184050224670)

price is 1600 USD.
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: testpoint1 on December 15, 2019, 05:17:16 pm
relist it:
https://www.ebay.com/itm/184082979500 (https://www.ebay.com/itm/184082979500)

updated to:

https://www.ebay.com/itm/184142834967 (https://www.ebay.com/itm/184142834967)
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: testpoint1 on January 10, 2020, 01:00:17 am
I also list one SRS PRS10 for sell, calibrated, with all designed accessories, 599 USD:

https://www.ebay.com/itm/Used-SRS-PRS10-Rubidium-Oscillator-with-all-interface-GPS-board-etc/184121607183 (https://www.ebay.com/itm/Used-SRS-PRS10-Rubidium-Oscillator-with-all-interface-GPS-board-etc/184121607183)
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: jpb on January 11, 2020, 12:37:55 pm
Hi testpoint1,

I'm not a customer yet as I already have 2 working Rubidiums and 4 GPSDOs but I follow your measurements with interest.

One question, what do you use as a reference in your measurements? You may have already stated this somewhere but I didn't see it.
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: testpoint1 on January 12, 2020, 04:00:54 pm
Hi testpoint1,

I'm not a customer yet as I already have 2 working Rubidiums and 4 GPSDOs but I follow your measurements with interest.

One question, what do you use as a reference in your measurements? You may have already stated this somewhere but I didn't see it.

verified by this:
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: testpoint1 on January 27, 2020, 11:21:02 pm
latest here:
https://www.ebay.com/itm/184142834967 (https://www.ebay.com/itm/184142834967)
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: Leo Bodnar on January 28, 2020, 08:33:11 pm
Quote
all the phase noise testing about OCXO is better than Rubidium in the web is a rumor
...
It's a well known governmental conspiracy.
Leo
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: nctnico on January 28, 2020, 08:42:27 pm
Quote
all the phase noise testing about OCXO is better than Rubidium in the web is a rumor
...
It's a well known governmental conspiracy.
Leo
From own experience: I 've seen a Rubidium being worse in terms of phase noise compared to a good oscillator. Putting a clean-up oscillator behind a Rubidium clock is a good solution to get a very clean clock with reasonable long term stability.
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: thinkfat on January 28, 2020, 09:05:15 pm
Quote
all the phase noise testing about OCXO is better than Rubidium in the web is a rumor
...
It's a well known governmental conspiracy.
Leo
From own experience: I 've seen a Rubidium being worse in terms of phase noise compared to a good oscillator. Putting a clean-up oscillator behind a Rubidium clock is a good solution to get a very clean clock with reasonable long term stability.

I don't quite see how a Rubidium-locked OCXO can possibly have less phase noise than the same, undisciplined OCXO. The servo loop will always introduce some disturbance.
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: jpb on January 28, 2020, 09:16:29 pm
Quote
all the phase noise testing about OCXO is better than Rubidium in the web is a rumor
...
It's a well known governmental conspiracy.
Leo
From own experience: I 've seen a Rubidium being worse in terms of phase noise compared to a good oscillator. Putting a clean-up oscillator behind a Rubidium clock is a good solution to get a very clean clock with reasonable long term stability.

I don't quite see how a Rubidium-locked OCXO can possibly have less phase noise than the same, undisciplined OCXO. The servo loop will always introduce some disturbance.
The point, I think, is that the OCXO has less phase noise than the rubidium while tracking its long term accuracy, the OCXO will not improve its own phase noise - just the long term stability or drift. Quartzlock sell a commercial version of this as do other companies I think.
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: Leo Bodnar on January 28, 2020, 09:39:36 pm
It's a well known governmental conspiracy.
Leo
From own experience: I 've seen a Rubidium being worse in terms of phase noise compared to a good oscillator. Putting a clean-up oscillator behind a Rubidium clock is a good solution to get a very clean clock with reasonable long term stability.
It was just irony. As per tradition.
Leo
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: testpoint1 on January 28, 2020, 11:24:53 pm
Quote
all the phase noise testing about OCXO is better than Rubidium in the web is a rumor
...
It's a well known governmental conspiracy.
Leo
From own experience: I 've seen a Rubidium being worse in terms of phase noise compared to a good oscillator. Putting a clean-up oscillator behind a Rubidium clock is a good solution to get a very clean clock with reasonable long term stability.

I don't quite see how a Rubidium-locked OCXO can possibly have less phase noise than the same, undisciplined OCXO. The servo loop will always introduce some disturbance.
The point, I think, is that the OCXO has less phase noise than the rubidium while tracking its long term accuracy, the OCXO will not improve its own phase noise - just the long term stability or drift. Quartzlock sell a commercial version of this as do other companies I think.

please tear down several OCXO and  Rubidium Oscillator (such as spectratime SRO), to compare its circult and infrastructure, then test the phase noise (do not forget use a CS reference),  paste here.
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: Leo Bodnar on January 29, 2020, 11:13:57 am
please tear down several OCXO and  Rubidium Oscillator (such as spectratime SRO), to compare its circult and infrastructure, then test the phase noise (do not forget use a CS reference),  paste here.
Are you confusing phase noise with timing stability?
Why on earth would you use Cs source as a phase noise reference?  It has just average phase noise performance.
Compare current top of the line Cs reference (https://www.microsemi.com/product-directory/cesium-frequency-references/4115-5071a-cesium-primary-frequency-standard#resources) with modern high quality OCXO (http://www.wenzel.com/model/btuln/)
Leo
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: testpoint1 on January 29, 2020, 03:32:06 pm
please tear down several OCXO and  Rubidium Oscillator (such as spectratime SRO), to compare its circult and infrastructure, then test the phase noise (do not forget use a CS reference),  paste here.
Are you confusing phase noise with timing stability?
Why on earth would you use Cs source as a phase noise reference?  It has just average phase noise performance.
Compare current top of the line Cs reference (https://www.microsemi.com/product-directory/cesium-frequency-references/4115-5071a-cesium-primary-frequency-standard#resources) with modern high quality OCXO (http://www.wenzel.com/model/btuln/)
Leo

if no frequency accuracy, hard to test the phase noise of a cesium standard, I ever check a E5505A test system to test the 5071A, they use another 5071A as frequency reference, any way, I just want to remind you, any atomic clock, is is not output from the Rubidium or Cesium cell, it is also from the crystal (temperature controlled).
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: testpoint1 on January 29, 2020, 04:02:03 pm
I would like to say here, if the phase noise testing using DUT as the frequency reference, I have no word; if test for 10MHz (usually is), 1Hz offest (dBc level), are you sure the 10MHz DUT is 10.000000MHz ? if the DUT frequency is not accurate (eg 10.000000 is 10.000002 MHz), any mean for test the "phase noise" of 1Hz  (10,000,001Hz) ?
I try to use a hign dynamic spectrum analyzer to test the parameter.
we used the atomic oscillator the demodulation wireless signal, we just care the frequency stability, sorry, never test the phase noise, if someone can test it, just paste here your test result and test diagram.
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: thinkfat on January 29, 2020, 04:12:23 pm
Not so easy to measure phase noise at these levels. You'll mostly measure your test instruments synthesizer. You need a rather complex setup to measure much below -100dBc/Hz

"TheSignalPath" on YT had a pretty interesting tutorial about this just recently.

https://www.youtube.com/watch?v=SOHjFtw0sgo (https://www.youtube.com/watch?v=SOHjFtw0sgo)

PS: The absolute frequency offset between the DUT and your instrument doesn't count, since the phase noise is always measured referenced to the signal.
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: Leo Bodnar on January 29, 2020, 04:31:12 pm
Only if you are using the wrong tool - like spectrum analyser.
Even 50 years old cheap and cheerful phase noise test kits will happily go to -170.. -180dBc/Hz if you feed them a good [=Wenzel or suchlike] clean reference.
Leo
P.S. Assuming 10MHz carrier ofc, not 1GHz
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: testpoint1 on January 29, 2020, 07:59:53 pm
Not so easy to measure phase noise at these levels. You'll mostly measure your test instruments synthesizer. You need a rather complex setup to measure much below -100dBc/Hz

"TheSignalPath" on YT had a pretty interesting tutorial about this just recently.

https://www.youtube.com/watch?v=SOHjFtw0sgo (https://www.youtube.com/watch?v=SOHjFtw0sgo)

PS: The absolute frequency offset between the DUT and your instrument doesn't count, since the phase noise is always measured referenced to the signal.

yes, BB60C can not test it, I try to use a SM200B to test it (I need to buy it, 13K USD), but, as a complete product (frequency standard reference), seems no mean to me to test it, since it is NOT a element (oscillator). I just care its frequency jitter wander, my focal point is 5G demoduation, not the universal electronics.
Title: Re: FS: high accuracy Rubidium Frequency Standard, with 10M, 60M, 0~20M and 1pps
Post by: thinkfat on January 29, 2020, 08:44:57 pm
Only if you are using the wrong tool - like spectrum analyser.
Even 50 years old cheap and cheerful phase noise test kits will happily go to -170.. -180dBc/Hz if you feed them a good [=Wenzel or suchlike] clean reference.
Leo
P.S. Assuming 10MHz carrier ofc, not 1GHz

Well yes, 1GHz seems to be Shahriars' idea of "low frequency". But the video still demonstrates the main point: if you haven't got a signal source that is way better than what you want to measure, you need to pull some pretty clever stunts. A Cs beam standard might be OK compared to a LPRO-class Rb standard, but that one is just -95dBc/Hz @10Hz. But a good OCXO should be well below that.

Random find on the net: -120dBc/Hz @10Hz
https://www.petermann-technik.de/fileadmin/documents/datasheets/Quartz-Crystal-Oszillators/ocxo/THT_LOW_POWER_OCXO-20.pdf (https://www.petermann-technik.de/fileadmin/documents/datasheets/Quartz-Crystal-Oszillators/ocxo/THT_LOW_POWER_OCXO-20.pdf)

I guess a spectrum analyzer is what an RF lab typically has available. Phase noise test set - pretty specialized type of gear, no?