[GPS_Standard] Re: My new controller

[Edwin B. Walker]

Bert wrote,

Hello Edwin,

The assumption here is that your GPS provides a clean and good 1PPS signal.

Looking at the info you provide, I think you forgot to set your VCXO tuning
slope to negative in the Montrol s/w. Double-check this.

As well, it looks like an oscillator that is not centered. If you are
railing at -4.9V and you are 3 Hz high, you will not be able to tune this
oscillator because the EFC (Vtune) pin can only tune +/-1Hz on the 10544.
You must re-adjust the trim-pot.

In Montrol s/w, Disable FLL Operation. Wait until the DAC Value field
becomes accessible. Re-center the DAC Value by typing in 512. Make sure you
press the Enter key after typing in a numerical value. Then adjust your
oscillator potentiometer to bring it back close to nominal frequency. Use
WWV (10MHz) to zero-beat as well. Finally, Enable FLL Operation again and
let it work.

Let me know...

Bert,
    I was never able to disable the FLL operations button with stability and 
thus follow your advice.

What else.........

I took the 10 MHz output of the HP-3801A, reduced it 15 dB and feed it into 
the control board.  The Montrol is showing a drifting between lock of FLL 
and holdover over a period of a minute roughly. This goes on hours on end.

Thanks for the help.

Ed