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LF: GPSDO experiments

To: [email protected], RSGB <[email protected]>
Subject: LF: GPSDO experiments
From: Wolfgang Büscher <[email protected]>
Date: Mon, 25 Jan 2016 23:03:29 +0100
Reply-to: [email protected]
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Greetings all,

My GPSDO prototype (with not just a frequency-locking, but also phase-locking loop) seems to run reliably now. But there is one thing which puzzles me, maybe someone here has more experience with 'commercial' VCOCXOs.
Mine was found at a hamfest, labelled "OFC MC598X4 - 010W  10.000000 MHz"
The tuning range, compared against GPS, is as follows:

 Vctrl = 0 V -> output frequency 10 MHz - 57 Hz
 Vctrl = 5 V -> output frequency 10 MHz
 Vctrl = 12 V -> output frequency 10 MHz + 80 Hz

So the 'electric' tuning range is - 5.7 ppm to + 8 ppm.
Isn't this a bit much for an oscillator labelled "10.000000 MHz" ?
I had expected a tuning range of a few Hz (since the frequency is specified with 1 Hz resolution on the label).

If anyone is interested in the PIC "C" sourcecode (written for a PIC16F1783), I can post it on a website as soon as some cosmetic issues (and curses about the PIC datasheet) have been fixed / removed.

All the best,
  Wolf DL4YHF .


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