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Re: Spectrum Scope via Sound card?




As others have mentioned, you can always feed audio into
a sound card and get spectra. With a suitable receiver
as a source of interesting noises, this is an excellent
way of wasting lots of time...I recently put together a
mindless little wrapper that obtained samples, fed them
to a mindless little FFT routine that I had written as
part of a school assignment (spectral estimation algor-
ithms - Welch, Yule-Walker/maximum entropy, 3rd order
recursion), and displayed the results in a waterfall
display. Much fun.

Sampling the IF is harder. If all you want is (say) a 10 kHz
slice of the IF, you can do sub-Nyquist sampling and look
at the aliases (just like a strobe light). Or use a
highly linear mixer to convert the slice of IF to baseband,
which amounts to the same thing (proof left as an exercise
to the student... :-).

Laura Halliday VA3LDH   "Que les nuages soient notre
Grid: FN03gs                pied a terre..."
                                   - Hospital/Shafte

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