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Discussion of precise time and frequency measurement

True Position GPSDP + Rb X72

Bob kb8tq

Sat, Sep 23, 2017 1:38 PM

If the main use is feeding test gear (and not direct synthesis) an Rb may do pretty well. Most
instruments assume a dirty reference signal and clean it up internally.

1 Hz at 20 GHz is 5x10^-11 most sources you measure up there will not be stable to 1Hz
at a 1 second gate. The Rb will be in this vicinity (frequency wise) second to second. Long
term drift will not be an issue with monthly calibration. It should be ok for temperature in
a constant environment.

Backing off to 1 Hz at 2 GHz takes you down to 5x10^-10. At that point the Rb is “plenty good
enough”. Keep it in a reasonably constant environment, calibrate it once a year and you’re fine.

Bob

On Sep 22, 2017, at 9:32 PM, Stephan Flor via time-nuts time-nuts@febo.com wrote:

The highest frequency I can generate is 2.5 GHz. My counter can measure 20 GHz, to 1 HZ. At the moment I'm have a frequency locking problem with the extension module in my HP 8660C, so I can't even get to 2.5 GHz, only 110 MHz at the moment. I gust got some extender boards, so I hope to have it fixed soon. The X72 gives me a solid 10.000000 MHz, I would like to see what I get when I use the Rb as a clock for the signal generator, at 2.5 GHz. I guess I only need to verify the calibration with the GPSDO, when I get it, and get it working. Then I can calibrate everything else.
So, to make a long answer short, I don't think I need the level of accuracy that these devices are capable of. I just have a neurotic need to try and make things as exact as I possibly can. Also, this is just a hobby, and learning experience for me, so I can take my time to work things out.Thank you,Steve

On Thursday, September 21, 2017 12:09 PM, Chris Caudle <chris@chriscaudle.org> wrote:

On Wed, September 20, 2017 3:44 pm, Stephan Flo via time-nuts wrote:

I just wanted a 10 MHz sync for my test equipment that was calibrated.
May be the GPSDO is all I need.

Even an undisciplined rubidium oscillator is going to be very close to
nominal 10MHz. You have never stated your desired precision that I have
seen. The X72 manual says that the output should be within 1E-9 in under
10 minutes, and within 5E-11 after 30 minutes. Does any of the equipment
you use have finer precision than that?

--
Chris Caudle

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Hi If the main use is feeding test gear (and not direct synthesis) an Rb may do pretty well. Most instruments assume a dirty reference signal and clean it up internally. 1 Hz at 20 GHz is 5x10^-11 most sources you measure up there will not be stable to 1Hz at a 1 second gate. The Rb will be in this vicinity (frequency wise) second to second. Long term drift will not be an issue with monthly calibration. It should be ok for temperature in a constant environment. Backing off to 1 Hz at 2 GHz takes you down to 5x10^-10. At that point the Rb is “plenty good enough”. Keep it in a reasonably constant environment, calibrate it once a year and you’re fine. Bob > On Sep 22, 2017, at 9:32 PM, Stephan Flor via time-nuts <time-nuts@febo.com> wrote: > > The highest frequency I can generate is 2.5 GHz. My counter can measure 20 GHz, to 1 HZ. At the moment I'm have a frequency locking problem with the extension module in my HP 8660C, so I can't even get to 2.5 GHz, only 110 MHz at the moment. I gust got some extender boards, so I hope to have it fixed soon. The X72 gives me a solid 10.000000 MHz, I would like to see what I get when I use the Rb as a clock for the signal generator, at 2.5 GHz. I guess I only need to verify the calibration with the GPSDO, when I get it, and get it working. Then I can calibrate everything else. > So, to make a long answer short, I don't think I need the level of accuracy that these devices are capable of. I just have a neurotic need to try and make things as exact as I possibly can. Also, this is just a hobby, and learning experience for me, so I can take my time to work things out.Thank you,Steve > > On Thursday, September 21, 2017 12:09 PM, Chris Caudle <chris@chriscaudle.org> wrote: > > > On Wed, September 20, 2017 3:44 pm, Stephan Flo via time-nuts wrote: >> I just wanted a 10 MHz sync for my test equipment that was calibrated. >> May be the GPSDO is all I need. > > Even an undisciplined rubidium oscillator is going to be very close to > nominal 10MHz. You have never stated your desired precision that I have > seen. The X72 manual says that the output should be within 1E-9 in under > 10 minutes, and within 5E-11 after 30 minutes. Does any of the equipment > you use have finer precision than that? > > -- > Chris Caudle > > > _______________________________________________ > 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. > > > > _______________________________________________ > 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.