If confused as to why the BFO had to be lowered to transmit an LSB signal after flipping from a 5mhz to a 19mhz bfo, then check out post?/g/BITX20/message/24724? That post gives everything in round numbers so the discussion is easier to follow. ?On stock radios, the BFO is around 11998500 hz. ?The crystal filter passband is about 3000 hz wide, and centered on around 11997000 hz. ?These frequencies are a bit below 12.0mhz since the crystal filter uses the series resonant frequency of the crystals (which is slightly lower than the parallel resonant frequency), and the BFO has added capacitance around the crystal. ??
Jerry, KE7ER
On Tue, May 16, 2017 at 09:20 am, Allard PE1NWL wrote:
can?t exactly remember the required BFO frequency for LSB (while the LO was on the high side of the IF), but I do remember it surprised me that it had to be lower than the original analog BFO frequency (I had expected it to be higher).
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