[GPS_Standard] Power Supply questions

[Bert, VE2ZAZ]

Hi Chris,

Welcome to the world of accurate frequency. Here are a few comments. 
First you should reduce the S sampling period to something like 16 to 
let the system find the sweet spot much faster. When you notice that the 
DAC adjustments alternate  (more or less) between going upward and 
downward, you are ready to use a much larger value. You are currently 
just wasting time slowly going through the DAC values. Note that you 
won't have to do this every time, just at the first time start up.

I don't know for how long you have had the OCXO powered up, but you can 
expect to see it drift (re-trace) for several days before stabilizing. 
This is typical of an OCXO that has been powered down for some time.

Did you try to center the OCXO with the coarse adjustment while 
zero-beating the 10MHz WWV station (with DAC value set to center)? 
Remember that the HP OCXOs can only tune electronically to +/- 0.5 Hz 
(if my memory does not fail me), so you may be sitting outside of the 
electronic tuning range. With WWV, you can do better than that with a 
bit of patience.

Have Fun.

Bert, VE2ZAZ
http://ve2zaz.net


On 02/12/2012 10:12 AM, Chris Howard w0ep wrote:
> After two years, I finally focused on getting this
> GPS standard working.  I have had all the parts
> for the past few months, but just didn't get
> around to putting it all together until yesterday
>
> I'm using the oscillator from a defunct HP counter,
> a Resolution-T GPS, built into a  2-U chassis which I picked
> up at a university's junk sale awhile back.
>
> The chassis was from some sort of heater controller from
> Kodak. It included a digital volt meter on the front panel
> which I have incorporated to watch the DAC voltage.
>
> I used power supply parts from the HP counter
> and the Kodak controller.  I am using a separate +/-5v
> supply from the Kodak unit instead of using
> the +5v derived onboard.
>
> It has been plugged in and running for 800 16-second
> samples and DAC voltage is slowly moving upward.
> No lock yet.
>
> I have a switchable RS-232 port that allows me to
> connect to either the GPS or the controller card.
>
> Still needed:  better GPS antenna connection (need
> to buy a crimper), better GPS antenna, bring bi-color
> LED to the front panel, and buy or make some 50 ohm
> BNC terminators for the unused ports.
>
>
>
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