USB output is lower because the Raduino flips from LSB to USB by moving the VFO from 5mhz to 19mhz, either of which when mixed with the incoming 7mhz result in a 12mhz product that can pass the IF filter. ? 5+7=12mhz ? 19-7=12mhz. ? Various parts, especially the diode ring mixer, may have less response at 19mhz than 5mhz. ?A better way to flip from LSB to USB is to move the BFO. ?Currently that is crytal controlled, and involves hacking L5 and C103. ?Using a second Si5351 channel to generate the BFO would allow the Raduino to control the BFO frequency. ?Moving the BFO up a few khz from 11.9985mhz to 12.0015mhz would flip the Bitx40 from LSB to USB, the VFO remaining at 5mhz. ?For now, perhaps you can just increase the drive level at R137 when transmitting on USB with the VFO at 19mhz. ?Yes, I'd bet it also affects RX. ?Though not all that noticeable, as the receiver has an incredible dynamic range. ?
On Fri, Feb 10, 2017 at 11:44 am, <KD2BBW@...> wrote:
That sucks USB output is lower. I wonder if it also affects RX as well?
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