I got my first PRS10 and am giving it a shakedown cruise, using the excellent interface board from "scs-ct". It locked in about 20-25 minutes and is running 0.025 Hz faster than my locked Z3805A. I pretty much bottomed the external ref pot trying to match the GPSDO, which also set off "too low" indicators in the SRS RbMon app. Attached is a screen grab of the app. How does this PRS10 look? What values should one be looking at when checking out newly-acquired PRS10? Walt

Hi Rb’s (like OCXO’s) take a while to stabilize after they are turned on. Yes, the magnitude of the change is way less for the Rb. It’s still the same sort of effect. I’d suggest letting the unit run for at least 24 hours (and better for a week) before worrying about setting in on frequency. Bob > On Feb 10, 2025, at 11:50 PM, Walt via time-nuts <time-nuts@lists.febo.com> wrote: > > I got my first PRS10 and am giving it a shakedown cruise, using the > excellent interface board from "scs-ct". It locked in about 20-25 minutes > and is running 0.025 Hz faster than my locked Z3805A. I pretty much bottomed > the external ref pot trying to match the GPSDO, which also set off "too low" > indicators in the SRS RbMon app. > > Attached is a screen grab of the app. How does this PRS10 look? What > values should one be looking at when checking out newly-acquired PRS10? > > Walt > > <PRS10-19511.png>_______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com

Hi, Bobs, My old PRS-10 takes about 10 minutes to lock up to the atomic line. Prior to that time the frequency error is *huge*. Once locked the frequency is still off, but by much smaller amounts, and it takes ten's of minutes to appear *pretty much* settled. I will say that whether or not the unit locks is a major indicator of the unit's health. *If the unit does not lock, expect* *to do considerable study and/or repair to make it usable.* Assuming that it does lock, if you want the best stability it can provide, expect to give it 3 or 4 days further settling in time (in my experience). Maybe longer if it has not been operated much for a long time. IIRC, the anticipated long term drift rate can be as high as 50 PPT per month. Mine always drifts upward in frequency, but the rate has usually been more like 20 PPT per month. Superimposed on the long term drift are kind of random frequency wanderings on the order of about 10 PPT. I built a home brew quadrature demodulator, whose I & Q outputs go to an o'scope set to its slowest roll-mode "sweep". I use a Rigol DS2202E 'scope, whose slowest roll-mode gives 14,000 seconds across the screen. If I'm really picky I'll set up the 'scope and quadrature demodulator about a week ahead of the need, and take a glance at the 'scope from time to time throughout the day, making small tweaks as I see fit. For the reference input to the demodulator I use the admittedly very noisy 10 MHz output of my CNS Clock II GPSDO. Because the noise on the output of that source is predominantly high frequency stuff (characteristic times of 10's of minutes), it is pretty easy to distinguish between the GPSDO's noise and that of the Rb under test. I tune the PRS-10 with a good quality 10-turn pot, aided by a DVM watching the slider voltage to help judge how much to turn the pot in response to a measured frequency error. The tune rate of the PRS-10 is nominally *about* 800 PPT per volt. Note that if you're really going for close setting, you'll need to watch the DSO's screen (off and on) for hours at a time to assess the actual error in the face of the random ramblings mentioned above. Dana Kerrville, TX On Tue, Feb 11, 2025 at 9:35 AM Bob Camp via time-nuts < time-nuts@lists.febo.com> wrote: > Hi > > Rb’s (like OCXO’s) take a while to stabilize after they are turned on. > Yes, the magnitude of the > change is way less for the Rb. It’s still the same sort of effect. > > I’d suggest letting the unit run for at least 24 hours (and better for a > week) before worrying about > setting in on frequency. > > Bob > > > On Feb 10, 2025, at 11:50 PM, Walt via time-nuts < > time-nuts@lists.febo.com> wrote: > > > > I got my first PRS10 and am giving it a shakedown cruise, using the > > excellent interface board from "scs-ct". It locked in about 20-25 > minutes > > and is running 0.025 Hz faster than my locked Z3805A. I pretty much > bottomed > > the external ref pot trying to match the GPSDO, which also set off "too > low" > > indicators in the SRS RbMon app. > > > > Attached is a screen grab of the app. How does this PRS10 look? What > > values should one be looking at when checking out newly-acquired PRS10? > > > > Walt > > > > <PRS10-19511.png>_______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe send an email to time-nuts-leave@lists.febo.com > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com