Another fix would be to move the VFO from 5mhz to 19mhz, then adjust the BFO down 3khz by adding capacitance at C103 (assuming you still want lower sideband operation). ?If that's confusing, then read that other thread where the bunch of women were talking: ??/g/BITX20/message/21911
Fixes both the birdie at 7.2mhz from the 5'th harmonic of the VFO and the image problem from the 4'th harmonic of the VFO. ?With a 19mhz VFO those harmonics are up in the low VHF, and nothing near them should be getting past the 7mhz bandpass-filter at L1,L2,L3. ?If the local TV stations are sneaking in, then time to start collecting tuna fish cans for use as shielding. ?Would be hard to get an analog VFO stable enough at 19mhz, but the Si5351 should do fine.
Oh, and ask John Smith how to adjust R136 to compensate for the greater losses at the diode ring mixer when transmitting with a 19mhz VFO: ?/g/BITX20/message/21948
Jerry, KE7ER
On Mon, Feb 13, 2017 at 02:27 pm, Jerry Gaffke wrote:
with possible fixes as per post ?21941.
?
