[GPS_Standard] Power Supply questions

[Chris Howard w0ep]

Thanks! I appreciate the encouragement.

I have made a couple of changes that gave me
quick improvement:

1) I worked up a small amp to boost my 1 PPM up to 5 volts.
2) I "discovered" that the HP oscillator needs negative
   tuning slope.

Now I am "locked" and chasing the warming up oscillator
back toward mid-range of the DAC voltage.





On 2/13/2012 7:11 AM, Bert, VE2ZAZ wrote:
> 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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>
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