The bandwidth is limited by our crystal filter. I couldn't make it wider than 25 KHz. If, instead, we had used phasing method, we could have achieved a full 96 KHz spectrum display. I discarded the phasing method for two reasons:
1. Performance: The phasing method critically depends upon keeping both channels flat with their phase and amplitude response throughout the 96 KHz pass-band. It becomes impossble to achieve more than 55 dB of suppression (the Elecraft KX3 promises just that). This means if you have a 599+20 dB CW signal 1 KHz away on CW, it will drown out the 559 signal you are trying to copy as the image will overlap.
2. Ease of Homebrewing: Many of us already ar comfortable with superhets. The sbitx architexture adds SDR backend to those radios.
If scan the commercial offerings, phasing radios are no longer being offered by anyone with the exception of KX2 and KX3.?
This said, apart from a few lines of code in rx_process and tx_process, there is very little to prevent the code from being adapted to a phasing radio.?
On Tue, Oct 24, 2023, 3:35 AM Mark Erbaugh <mark.election@...> wrote:
The sample rate appears to be 96 kHz, but the bandwidth is only 24 kHz. Shouldn't it be 48 kHz, half the sampling rate? Is this due to the overlap-discard processing? -- 73, Mark, N8ME
