Re: SDR and Ubitx freq not the same.

Arvo W0VRA

To compare the frequencies of the µBITX and the RSP1A, which I use together, I did an FT8 transmission with the µBITX set to 20M, 14.074MHz and the FT8 signal at 2000Hz.  Without an RX antenna connected to the RSP1A, there was still a strong signal showing up in the WSJT-X FT8 screen.  So the PC with the µBITX was doing the 14.074MHz + 2000 Hz, and the laptop with the RSP1A running FT8 was showing that signal as 14.074MHz + 1986 Hz.

I then applied the CEC principles of calibration to the µBITX and got them within 1 Hz, sometimes 0 Hz.

They move around a little bit, probably because their temperatures are changing and affecting them differently.

Also, if someone is using a transceiver with a common oscillator for RX and TX (like another µBITX) and responds to you on FT8 with their frequency the same as yours, you'll see the same difference between the SDR and the µBITX.

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