[Elecraft] K3 15khz 2nd IF?

[David Woolley]

n2ey at aol.com wrote:

> The lower you go, the better, because you get more samples per Hz of 
> signal. (If you are sampling a 15 kHz signal 150,000 times per
> second, that's 10,000 samples per Hz, but if you were to sample a 150
> kHz signal the same number of times per second you only get 1000 > samples per Hz.) All else being equal, more samples per Hz is better, as
> is more bits per sample.

This doesn't make sense to me.  In a quadrature system, you only need to 
sample at a sampling *rate* equal to the bandwidth (you meet the Nyquist 
condition because the I and Q samples effectively double the rate).  In 
practice you would want to sample based on the skirt bandwidth, not the 
nose bandwidth.

I believe some DSP based receivers actually sample a band limited IF 
directly, at the bandwidth dictated sampling rate.

Going low probably makes the whole process more reliable.
-- 
David Woolley
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