[amsat-bb] Re: SSTV Algorithms?
cptcurt at flash.net
Fri Oct 17 06:43:47 PDT 2008
Nope...you got it just right!
As Simon pointed out, its all about knowing what information you want to
get from the "re-constructed" wave. If you want all the detail, you
have to sample at least 2f of the highest harmonic content. Square
waves with fast rising leading edges are a real mutha!! Its why we sold
alot of multi-gig one-shot samplers!
For repetitive waveforms, averaging with a sample rate much slower and
randomly distributed across the signal results in good reconstruction
but is not "realtime" or one-shot capable.
Nigel Gunn G8IFF/W8IFF wrote:
> According to Mr Nyquist (I think that's who it was) you only need to sample at twice the highest frequency contained in the sampled waveform but
> remember that here we are talking about twice the frequency of the highest harmonic contained in the waveform so 8KHz wouldn't be sufficient for
> a 4KHz square wave but would be sufficient to reconstruct a 4KHz sine wave..... or is my theory screwed up as well?
> Gordon JC Pearce MM3YEQ wrote:
>> Hmm. That's not quite true.
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