Hello,
I am interested in building a one-off PIC controlled portable ham radio receiver, specifically oriented towards a low cost direct conversion design optimized for CW. I have experience with PICs (and other MCUs) and analog and RF but very little ham experience (I am not a ham - or not yet - I am working on my code practice).
I am looking at some ideas for a simple but above average quality (processing, technical specs) direct conversion receiver aimed at 7 MHz and mostly CW, and later expandable to 3.5 and 14 MHz.
While trying to solve the problem of pile-ups with a relatively wideband audio receiver, the following questions came up:
- Does panorama (stereo) processing of audio in a direct conversion receiver help with separation, in despite of the image frequencies presence ?
- Does IQ processing in a direct conversion receiver solve the image problem ? (i.e. two channels 90 degrees out of phase). Is anyone using an IQ direct conversion receiver with DC (or low frequency) output to amplitude and/or modulate a tone oscillator for receiving CW ? (note that this solves the image problem imho).
- I think that using dynamic compression on the audio signal would help a lot with pileups. In a pileup there may be signals with 50 dB or more of relative loudness. I think that using a dynamic compressor can reduce that to 10-20 dB if AGC is also used. Yet, I was unable to find references on this. Is there a reason for not using dynamic compression with CW signals in a pileup (besides the difficulty presented by the fluctuating amplitude etc). Would a compressor not help in general when several signals are in the audio band, and each fades separately, thus confusing AGC ?
- At least one commercial receiver (Elekraft) uses a PIC for frequency readout. Would a Weeder style counter create too much noise if used directly next to a sensitive receiver circuit ?
thank you for any answers or pointers, Peter P.