Ham radio + PIC + audio processing

[[email protected]]

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.

 

[David Harmon]

On 6 Apr 2007 00:14:37 -0700 in sci.electronics.design,
[email protected] wrote,

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).

What country are you in, that still has a code requirement?

 

[[email protected]]

On 6 Apr 2007 00:14:37 -0700 in sci.electronics.design,
[email protected] wrote,


What country are you in, that still has a code requirement?

*I* have a code requirement, but that is not the point. The point is
the exercise and later slow dx digital modes.

thanks,
Peter P.