06-29-2019, 01:42 PM
The local oscillator in the modified tuner is higher in frequency than the incoming signal. The beat frequency is the IF of the tuner and is adjusted to fit in the tuning range of the old FM band. Thus the higher the desired incoming frequency, the lower the beat frequency and you have to tune lower on the FM dial. One other thing to note is that the band pass of the TV tuner IF has to be close to 8 mhz wide or the ends of the FM tuner dial would fall off in sensitivity. the guy doing this has scope traces showing the wide bandwidth.
