Re: [time-nuts] OCXO Vref (in)stability plot
In message 7d58cf6b-25de-4e7d-9570-e512a22aa...@email.android.com, Didier wri tes: What is the bandwidth of the measurement? Very low. The measurements show here are made with an RC lowpass filter (5k/1µF) on the output, but it doesn't change the statistical properties of the noise at all. Settings on the HP3458A (NPLC,NDIG etc) has no effect either. I suspect it is the oven-power leaking through. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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.
Re: [time-nuts] OCXO Vref (in)stability plot
In message 5174699e.9060...@sasktel.net, Ed Palmer writes: I think that Vref is derived from the internal voltage regulator that powers the oscillator. Is it possible that any noise will appear on both and therefore, they'll cancel each other out? That could even reduce power supply sensitivity. I guess that is a remote possibility, but quite frankly, I doubt it. I think it far more likely that 10-20 microVolt is simply good enough for what OCXO's are/were[1] normally used for. [1] This is a pretty old OCXO. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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.
Re: [time-nuts] OCXO Vref (in)stability plot
Poul-Henning, your finding is quite interesting. I would like to replicate your measurements on some other voltage sources and Vref sources. Could you please elaborate on the setup, settings and acquisition process? Thank you, Jochen ___ 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.
Re: [time-nuts] OCXO Vref (in)stability plot
In message trinity-7a7ee757-89f7-4b92-8884-9435668fef15-1366646349138@3capp-gm x-bs21, Jochen Frieling writes: your finding is quite interesting. I would like to replicate your measurements on some other voltage sources and Vref sources. Could you please elaborate on the setup, settings and acquisition process? There really isn't anything to it: Power the OCXO from a good clean supply (HP6626A in my case), measure the voltage on the VREF pin with the best voltmeter you have. In my case a HP3458A with NDIG=8, NPLC=20 -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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.
Re: [time-nuts] OCXO Vref (in)stability plot
On Mon, 22 Apr 2013 16:13:17 +, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message trinity-7a7ee757-89f7-4b92-8884-9435668fef15-1366646349138@3capp-gm x-bs21, Jochen Frieling writes: your finding is quite interesting. I would like to replicate your measurements on some other voltage sources and Vref sources. Could you please elaborate on the setup, settings and acquisition process? There really isn't anything to it: Power the OCXO from a good clean supply (HP6626A in my case), measure the voltage on the VREF pin with the best voltmeter you have. In my case a HP3458A with NDIG=8, NPLC=20 I have used the same technique to optimize 0.1 to 10 Hz noise in low noise amplifiers, references, and power supplies. Conveniently the standard deviation is equal to the RMS so the calculations are easy and I had good agreement with the datasheet values of various parts. ___ 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.
Re: [time-nuts] OCXO Vref (in)stability plot
The OCXO's Vref has 18 microVolt RMS noise I used my HP3458A to measure the stability of the Vref output from an IsoTemp OCXO-107 and the results were anything but stellar: Neat. Thanks. What's the spectrum look like and what's the bandwidth of the filter inside the OCXO? How much of that noise is going to cause trouble? -- These are my opinions. I hate spam. ___ 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.
Re: [time-nuts] OCXO Vref (in)stability plot
I think that Vref is derived from the internal voltage regulator that powers the oscillator. Is it possible that any noise will appear on both and therefore, they'll cancel each other out? That could even reduce power supply sensitivity. You could test that by measuring ADEV with an EFC pot powered by Vref vs. powered by an external quiet supply. Ed On 4/21/2013 2:47 PM, Poul-Henning Kamp wrote: Ok, this surprised me a LOT! I used my HP3458A to measure the stability of the Vref output from an IsoTemp OCXO-107 and the results were anything but stellar: The OCXO's Vref has 18 microVolt RMS noise For comparison my HP6626A power-supply has 2 microVolt RMS noise. Obviously, the Vref only has to be good enough to not be a relevant source of noise when used on the EFC input. If the OCXO has a EFC sensitivity of 10PPM/Volt, then a microVolt more or less means a 1e-11 change in frequency. The Vref is also quite sensitive to the OCXO supply voltage, but since it was powered by the HP6626A, that's not where the noise comes from. ___ 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.
Re: [time-nuts] OCXO Vref (in)stability plot
What is the bandwidth of the measurement? It may be some broadband noise that is filtered by the OCXO Didier KO4BB Poul-Henning Kamp p...@phk.freebsd.dk wrote: Ok, this surprised me a LOT! I used my HP3458A to measure the stability of the Vref output from an IsoTemp OCXO-107 and the results were anything but stellar: The OCXO's Vref has 18 microVolt RMS noise For comparison my HP6626A power-supply has 2 microVolt RMS noise. Obviously, the Vref only has to be good enough to not be a relevant source of noise when used on the EFC input. If the OCXO has a EFC sensitivity of 10PPM/Volt, then a microVolt more or less means a 1e-11 change in frequency. The Vref is also quite sensitive to the OCXO supply voltage, but since it was powered by the HP6626A, that's not where the noise comes from. Plot attached... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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. -- Sent from my Nexus 7 tablet. ___ 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.
