At 08:05 AM 12/17/2005, Robert McGwier wrote:
Jim:
Sorry I was not clear:
2 transmit ports could output processed audio for monitoring and 2 could
output 11025 KHz for sending to the radio. It will have the hookup we
currently use for the Delta 44 but we are sending the same thing to both
ports, one has AF gain control on it for monitoring and the other has PWR
control on it. Otherwise, it is the same audio.
This will move us away from the 1/f, DC mixing components, etc we
currently get (at a low level but present nevertheless) and it will move
the image from (say) a few Hz to 20+ Khz away making image rejection more
easy on TX.
Certainly, getting away from DC-50Hz is a "good thing", but isn't that
already the case? My experience with modulating using the on-mobo sound
interface has been that it's really, really bad close to DC. (probably
because there's a DC block in there, and a not too well defined load
impedance). I had always assumed that the PowerSDR software did the ssb
upconversion to the 11kHz IF from the audio input.
Aren't you doing your Tx at the same DDS frequency as the Rx (where the IF
is 11kHz)?
Or, does the software switch the DDS frequency when you go from Tx to Rx?
(which raises a whole host of issues with spurs and the like).
