🚀 go-pugleaf

In article <39884@ut-emx.uucp> tkelman@emx.utexas.edu (Todd Kelman) writes:
>Problem:  I have a signal with frequency components from 20Hz - 3000Hz, that
>I need to shift to fit in a range from 300-3400Hz. 

	While you could shift the whole signal (as you described) in
one go, it might be just as easy to shift it in pieces; filter out
the 20 Hz-300 Hz and upshift it with a 3400 Hz local oscillator;
the lower sideband (3100 Hz to 3380 Hz) can simply be added to the
original signal.

	A perhaps more straightforward approach (to make the filters
less tricky) might be to mix up with a 450 kHz LO, filter the unwanted
sideband with a standard IF crystal filter (cheap mass produced ones
for AM radio are available from various places), then mix the
whole thing back down with a 446 kHz LO.  Mixers can be very simple
for this sort of thing (because the spurious double-LO frequency
is pretty darned far from the range of interest).  You'd be using the
simplest of mixers (maybe even just a diode), so the fact that there's
two wouldn't be much of a problem.

	John Whitmore