I dont know if many people are using the Raspi 3 and the QRP Guys filter hat hat, but when I put it on my chums Spectrum analyser it displayed a spike at just over 10Mhz which disappeared on my transmission of 14.097100Mhz - returning once the transmission ceased. we tried all kinds of things to attenuate this but I fear it was some kind of artifact from the Raspi - anyone else noticed this?