On 9/30/05, Frank Brickle <ab2kt@...> wrote:
--- In softrock40@..., Ramakrishnan Muthukrishnan
11025 * 2 = 22050.
22050 * 2 = 44100.
11025Hz is the center of the presumed "good" passband on typical
soundcards capable of handling audio CD rates.
You don't want to downconvert to 0 because most soundcards have
bandpass filtering that roll off towards 0 and the Nyquist frequency.
If you downconverted to 0, you'd be filtering off most of the signal
before it got to your signal processing.
Therefore you downconvert such that the signal of interest is in the
"best" part of the soundcard passband.
Thanks Frank. That's quite clear.
Is it correct to assume that "if there is no sound card, and if we
have a higher sampling rate ADC, we can see more portion of the band"?
Or rephrasing it this way - What would be the passband of the signal
output from the QSD ?
--
73 - Ramakrishnan, VU3RDD
Ramakrishnan Muthukrishnan