I just remembered. The 40 mhz crystal filter is sharp on the upper sideband and shallow on the lower sideband.
Using it as an upper sudeband filter will make the opposite sideband kuch shallower. This is the way of all ladde filters, they are also called LSB filters (imagine the filter with inductors in place of the crystals, it becomes a ln LPF).
On Wed, Oct 25, 2023, 6:22 AM Mark Erbaugh <mark.election@...> wrote:
Well, I hacked in the code to change the Local Oscillator (clock 1) between 40,035,000 (current default) for USB modes and 39,987,000 for LSB modes.
Seems to work.? I still need to adjust the spectrum and waterfall.
One thing: I was looking for a single place in the code to detect mode change, but could not find one. The mode appears to be changed in both set_mode (sbitx_gtx.c) and sdr_request (sbitx.c), so currently I'm changing the LO in both places.
