VFO with QLG1 GPS discipline working? #vfo #gps #qlg1

Bob Benedict, KD8CGH

I recently built a QRP Labs VFO kit and a QLG1 GPS. I had previously built a U3S and QLG1 that appeared to work as expected. The VFO appears to work as expected, but the I don't see any evidence that the QLG1 provides any correction.
Gear: VFO with QLG1, GPS mode 2, 9600, display line 2: A 3D (valid 3D data)
Test: RSP1A SDR receiver with .5 ppm TXCO tuned to 9,999,000 Hz to monitor WWV at 10 MHz and VFO at 10.1 MHz. Signal levels adjusted to be comparable. SDR output fed to fldigi with new FMT test that monitors two signals. WWV set as "reference" and VFO as "unknown".
I observed that the VFO did not correct to 10.1 MHz. WWV appears stable, but the VFO drifted +8 Hz and never corrects. Below I attach a few of the many tests with similar results.
The first image shows the VFO initial drift.  At about minute ten I adjusted the base to bring the line back on the graph (+/- 4 max chart range). Letting it run longer showed a continued long, slow drift up.
The second image is a graph of a test when I ran the VFO without the GPS and then turned it on at about minute 11. The GPS display line shows "A 3D", but it appears to have no effect on the VFO.

Any hints how to get this to work?


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