[time-nuts] Freq cal to 1ppm without GPSDO

[WB6BNQ]

John,

Besides the M12 receiver you will need an interface board to provide a 3.3 volt
regulator for the M12, a 5 volt regulator and some 74c04's or some such to
provide the 1pps interface and drive levels to a MAX232 chip for a RS232
interface.  Then you will need to build up the Brooke Shera comparator and
control board to interface a high quality oscillator in order to duplicate what
is already provided in the Trimble Thunderbolt GPSDO.

The Brooke Shera system gives you a part by part insight on what goes on in the
Thunderbolt.  However, there is a bit of work to get the Shera system up and
running.  The advantage of the Thunderbolt is that it is pretty much a
plug-n-play unit.

73....Bill....WB6BNQ


John Beale wrote:

> Hi Murray,
>
> Thanks to you and the others for your replies. After some more HF reception
> problems here, I have come to the same conclusion as you. I found an Oncore
> M12+ timing GPS is available pretty cheap from Hong Kong, so that's my plan.
>
> best regards,
> John Beale
>
>  > 1. My best advice is to get hold of a cheap GPS module with a 1pps
> (seconds pulse) output. Connect it up, and when you have a fix, use the
> 1pps to trigger your digital oscilloscope. Set the timebase to 1us/div to
> start with, and ultimately 100ns, and observe the 10MHz output of your
> TCXO. You will see the waveform drifting slowly. Counting how long it takes
> to slip one cycle will tell you how far off the TCXO is. If you have a
> counter with Time Interval mode capability, you could use that, using the
> GPS to start and 10MHz to stop, again observing the drift.
>
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