Re: interference from SW broadcasters above 7200
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Jerry I measured it this morning!
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500Hz shift in VFO produces a shift of 2500 Hz in the birdie! As the frequency shifts even more the birdie goes way beyond the 3KHz limit as I would imagine. Guess it is mixing somewhere and produces a beat not on either side of the zero! Cheers Raj But I think the birdie most folks are seeing at 7.2mhz is independent from these image signals. The birdie is likely the 5'th harmonic of the VFO mixing with the 2'ed harmonic of the BFO, with possible fixes as per post 21941. 5*(12-7.2) = 2*12 This could be verified by determining how fast the tone of the birdie changes as the VFO frequency is advanced, should be 5 times as fast as a normal 40m signal. Remarkable that both issues zero in on 7.2mhz like that. |
Raj vu2zap