View Single Post
  #7   Report Post  
Old September 10th 06, 05:04 PM posted to rec.radio.amateur.homebrew
ken scharf ken scharf is offline
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 182
Default Intermediate Frequency

i3hev, mario held wrote:
Dave Platt wrote:

As I understand it, in order to do SSB via direct conversion, you must
use a modern version of the old IQ phasing technique. ...


that's correct
the problem here is that you need a phasing filter offering a constant
(and precise) 90 degrees phase shift all over the receiver band, and
that can be tricky to do...

These days, of course, you can apply the phase shift by converting the
two baseband signals to digital format...


well, you're opening doors to digital radio
But, AFAIK, the actually attainable dynamics does
not seem to incite enthusiastic greetings...

IQ phasing detection (AKA image reject mixers) are only necessary
if you want to build a single signal receiver (a good idea).
Many modern DDS chips provide a way to generate perfect quaditure
outputs and by using DSP you can combine the resulting quaditure
af outputs into a single signal. One way to do this on the cheap
is to have a pc sound card sample the two signals.