I went to OZ7SAT today to do some measurements on the receiver boards. I wanted to see how the sensitivities compare to that of the WBX receiver that I have measured earlier using a CW signal and SSB receiver. The criteria was again to find the weakest signal that I could both hear and see on the spectrum scope and that I would be able to decode if it was a Morse code transmission. The limiting parameter is actually the spectrum scope, because I can hear tones much weaker than what is visible on the 512 channel FFT scope.
My measurements started with some bad news: My RFX1200 appears to be broken. When I start the software it can not tune to the target frequency.
The other daughterboards behaved much better. I measured both the TVRX and the LFRX receivers. I was very curious about the LFRX since it contains no active elements. Still, I could hear signals between -95 and -102 dBm depending on the frequency. This corresponds to 1.8 to 4 µV and that’s not bad for an ADC+PGA (yes, the gain was at the maximum 20 dB).
The TVRX did good too, in fact much better than I expected. I had no trouble hearing signals at -125 dBm that is 0.12 µV. I used a gain setting of 71 dB, which seemed to give best SNR.