Right, had my U3S have 6 minutes calibration between transmissions over night. Still the frequency is 20Hz low when frequency display is reading 28.000.890 and still has the 20Hz power-on 'tail'. Chris's grabber in not 20 Hz out.

I'm running out of options here. Do I assume there is something really wrong and chuck in the towel for 10m QRSS? I don't think there's anything left to adjust.

Is it worth getting the?OCXO/Si5351A synthesizer module kit? Is that still frequency stabilised by the QLG1 GPS receiver module kit or is that not necessary?

Was having a lot of fun with the U3S, but maybe mine is starting to fail...

73,

Ian, G4JQT