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Discussion of precise time and frequency measurement

Re: [time-nuts] OCXO inside the FEI AN/URQ-23

ewkehren

Tue, Jul 25, 2017 4:12 PM

Sent from my Galaxy Tab® A
-------- Original message --------From: Tom Van Baak tvb@LeapSecond.com Date: 7/25/17 11:37 AM (GMT-05:00) To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] OCXO inside the FEI AN/URQ-23
Bert,

In the early days of time-nuts the URQ-10, and especially the URQ-23, were highly sought after because of their reported stability. By now they are quite rare. Do you have one?

If it's important I can dig one out from the closet and run tests for you.

"Question if it is frequency or ADEV".

I'm not sure what you mean. There is no such thing as "frequency" vs. "ADEV".

/tvb

----- Original Message -----
From: "Bert Kehren via time-nuts" time-nuts@febo.com
To: time-nuts@febo.com
Sent: Tuesday, July 25, 2017 7:48 AM
Subject: [time-nuts] OCXO inside the FEI AN/URQ-23

Has any one run tests of the OCXO inside the AN/URQ-23. Data in the manual
looks promising. Question if it is frequency or ADEV
Bert Kehren

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Thanks I have 2. Will run some tests. In my opinion ADEV does hide changes in Frequency and we see it when we compare ADEV plots with at the same time frequency measurements. We see it with your plots on the Tbolt. The URQ shows frequency specs 2E-12 most likely ADEVBert Sent from my Galaxy Tab® A -------- Original message --------From: Tom Van Baak <tvb@LeapSecond.com> Date: 7/25/17 11:37 AM (GMT-05:00) To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Subject: Re: [time-nuts] OCXO inside the FEI AN/URQ-23 Bert, In the early days of time-nuts the URQ-10, and especially the URQ-23, were highly sought after because of their reported stability. By now they are quite rare. Do you have one? If it's important I can dig one out from the closet and run tests for you. > "Question if it is frequency or ADEV". I'm not sure what you mean. There is no such thing as "frequency" vs. "ADEV". /tvb ----- Original Message ----- From: "Bert Kehren via time-nuts" <time-nuts@febo.com> To: <time-nuts@febo.com> Sent: Tuesday, July 25, 2017 7:48 AM Subject: [time-nuts] OCXO inside the FEI AN/URQ-23 > Has any one run tests of the OCXO inside the AN/URQ-23. Data in the manual > looks promising. Question if it is frequency or ADEV > Bert Kehren _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.

Tom Van Baak

Tue, Jul 25, 2017 4:50 PM

In my opinion ADEV does hide changes in Frequency and we see it when
we compare ADEV plots with at the same time frequency measurements.

On purpose ADEV reduces hundreds, even hundreds of thousands of measurements to a single number. If this is what you mean by "hide" then ok. In my opinion, ADEV does not hide changes in frequency; it statistically summarizes them in a standard way.

In general one should always look at phase residual or relative frequency strip charts before using ADEV. Another trick is using Stable32's DAVAR or TimeLab's multi-trace feature, both of which will expose variations in ADEV across a large data set. Or use histograms, etc.

However, as you seem to imply, if you are seeing unexpected differences between frequency measurements and time (phase) measurements or between freq / time and ADEV statistics, then your measurement system(s) are broken. With only a single DUT, if different "at the same time" measurement systems report different results, then that's a smoking gun to find which measurement system(s) is failing you.

The URQ shows frequency specs 2E-12 most likely ADEV.

See Table II on Page 9 of the manual [1].

/tvb

[1] http://mil-spec.tpub.com/MIL-T/MIL-T-28816/MIL-T-2881600009.htm

-------- Original message --------
From: Tom Van Baak tvb@LeapSecond.com
Date: 7/25/17 11:37 AM (GMT-05:00)
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Subject: Re: [time-nuts] OCXO inside the FEI AN/URQ-23

Bert,

In the early days of time-nuts the URQ-10, and especially the URQ-23, were highly sought after because of their reported stability. By now they are quite rare. Do you have one?

If it's important I can dig one out from the closet and run tests for you.

"Question if it is frequency or ADEV".

I'm not sure what you mean. There is no such thing as "frequency" vs. "ADEV".

/tvb

----- Original Message -----
From: "Bert Kehren via time-nuts" time-nuts@febo.com
To: time-nuts@febo.com
Sent: Tuesday, July 25, 2017 7:48 AM
Subject: [time-nuts] OCXO inside the FEI AN/URQ-23

Has any one run tests of the OCXO inside the AN/URQ-23. Data in the manual
looks promising. Question if it is frequency or ADEV
Bert Kehren

> In my opinion ADEV does hide changes in Frequency and we see it when > we compare ADEV plots with at the same time frequency measurements. On purpose ADEV reduces hundreds, even hundreds of thousands of measurements to a single number. If this is what you mean by "hide" then ok. In my opinion, ADEV does not hide changes in frequency; it statistically summarizes them in a standard way. In general one should always look at phase residual or relative frequency strip charts before using ADEV. Another trick is using Stable32's DAVAR or TimeLab's multi-trace feature, both of which will expose variations in ADEV across a large data set. Or use histograms, etc. However, as you seem to imply, if you are seeing unexpected differences between frequency measurements and time (phase) measurements or between freq / time and ADEV statistics, then your measurement system(s) are broken. With only a single DUT, if different "at the same time" measurement systems report different results, then that's a smoking gun to find which measurement system(s) is failing you. > The URQ shows frequency specs 2E-12 most likely ADEV. See Table II on Page 9 of the manual [1]. /tvb [1] http://mil-spec.tpub.com/MIL-T/MIL-T-28816/MIL-T-2881600009.htm -------- Original message -------- From: Tom Van Baak <tvb@LeapSecond.com> Date: 7/25/17 11:37 AM (GMT-05:00) To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Subject: Re: [time-nuts] OCXO inside the FEI AN/URQ-23 Bert, In the early days of time-nuts the URQ-10, and especially the URQ-23, were highly sought after because of their reported stability. By now they are quite rare. Do you have one? If it's important I can dig one out from the closet and run tests for you. > "Question if it is frequency or ADEV". I'm not sure what you mean. There is no such thing as "frequency" vs. "ADEV". /tvb ----- Original Message ----- From: "Bert Kehren via time-nuts" <time-nuts@febo.com> To: <time-nuts@febo.com> Sent: Tuesday, July 25, 2017 7:48 AM Subject: [time-nuts] OCXO inside the FEI AN/URQ-23 > Has any one run tests of the OCXO inside the AN/URQ-23. Data in the manual > looks promising. Question if it is frequency or ADEV > Bert Kehren