On Fri, 25 Mar 2005 23:15:46 -0500, "Leland C. Scott"
wrote in :

snip
For a filter, you can run both sides
of a stereo equalizer in series, and it can even tune different audio
freqs.

The stereo equalizer idea wouldn't work, bandwidth isn't narrow enough.
However a cheap DSP based single frequency audio band filter would do the
job. As cheap as these things, DSP chips, have become it shouldn't be a big
deal.


Just for kicks I tried an old Rat Shack 10-channel (left and right
channels in series) while tuned to a CW pileup on 80m. Worked OK, you
could differentiate one tone from another, but it passed a lot of
noise. I also tried a 31-channel Sunn but the thing broke out into
oscillation...:-0 Maybe stereo equalizers aren't such a good idea.


After that, all you would need is a tone detector with a light
bulb. So the most expensive piece of equipment is already made and is
pretty common, while the other two pieces could be built from a kit by
just about anyone with a soldering iron.

The detector, indicator, device could be incorporated in to the DSP filter
assembly.


Come to think about it, how about just a 567 or 4046? Either chip
would probably do it as long as the radio doesn't drift too much. And
if I'm not mistaken, both have a VFO on the chip. So a CW 'adapter'
could be a single-chip project -- no DSP required.

But I see a big problem -- there will no doubt be some numbskull who
would turn up the oscillator all the way and key up in AM on a radio
with a disabled limiter. Gawd, think of the splatter something like
that could cause.....






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