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Re: U3S drift/chirp - again!

 

Ian,
I did some measurements on my U3S with OCXO tonight. Calibrated a warm TS590S (TCXO) on air 5MHz and to my rubidium 10MHz to within 1Hz in WSJT-X. Condx bad for 30/20m beacons tonight.
Listened with the 590 (small antenna on the bench) on the 27MHz crystal and found it to be slightly off for some reason, the U3S repeatedly calibrated to 26 998 040 and the 590/wsjtx said 26 998 048 (0.3ppm). This is about the same 3Hz someone reported for the GPS ProgRock at 10MHz, IIRC it was 2Hz low ? Anyways, this might be within drift of all components here.
Started some WSPR2 transmission on 6m without LPF and into a dummy load, 60sec calibration and 60s idle (park mode 3). The 27MHz frequency variation was less than 1Hz, a fast jump up some 0.5Hz when the WSPR started and peaking in the end of the transmission. Slowly going down in the calibration (almost flattened out) and then lowered some 0.1Hz more when idling and returning to 0.2Hz above the last idling frequency. Repeated cycles made the frequency return to almost the same as the previous.
Anyways, the OCXO is a quite good module if you want to have a stable reference on the higher frequencies with U3(S).

If someone wants better accuracy and logs I can perhaps throw together the HP53131 running on the rubidium and listening to Clk1 output from the OCXO in the U3S. But Clk1 is only enabled during idling/parking?
Or if there's some better way to make the U3S keep calibrating and outputting a 10MHz (6.75MHz?) that I can measure with the HP.
Maybe I can try to mount the OCXO on the ProgRock and having it connected to the GPS... tell me if this is interesting to someone other than myself :D
73's
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