--- In softrock40@..., KY1K <ky1k@p...> wrote:
OK, now I'm really confused...........
Welcome to the club :-)
If I fire up my softrock-40 on my computer that has the ability to
sample at 48 Khz (with the center frequency at 7056 KHz)....
Yes to all.
I thought only a 96 Khz bandwidth card would give a 48 KHz spectral
display....
Here's the deal. Shannon's Theorem tells you that you need 2N bits/sec
to capture N bits of bandwidth. If you're only sampling the real part,
ie in mono, that means you need to sample at 2F to capture a bandwidth
of F.
However, since the QSD samples in Quadrature, you're getting a
*complex* signal, ie stereo. Those are your 2N bits, 2 channels x N
bits/channel. Therefore with complex sampling you can sample at F to
capture bandwidth F.
It doesn't save anything in terms of the *total* bandwidth, which is
still 2N bits, but it lets you use D/A converters only half as fast.
Except you need two of them.
73
Frank
AB2KT
