I notice that my Raspberry Pi 10mW sometimes appears at two different frequencies at the same time at the same rx station, both being within band and LPF.

In my current 60m tx I do not have a coupling capacitor, only the Hans Summers' LPF before an UNUN; over Christmas on 20m I used the TAPR shield and 100mW - same phenomenon locally.

Does anyone have any thoughts about whether there is intermodulation at the receive end, or a weaker signal being transmitted?

The answer might lie in putting the Pi output through a spectrum analyser. Has anyone done this, and if so, what was the power of the harmonic, if there was one?

73 de andy g0sfj andythomasmail AT yahoo DOT uk