No. That is what I meant by "we are not doing this correctly". The
issue is, and always has been, the monitoring demands of the
audiophiles and many others. When we had two port (single stereo
channel output) cards, we could not provide both monitoring and
offset. You are quite correct that it is a good thing, and we
should've already done it. The single stereo card folks will just have
to lose out on this immediate and large improvement in TX quality. The
four port cards allow us to do this easily.
Bob
Jim Lux wrote:
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).
--
Laziness is the number one inspiration for ingenuity. Guilty as charged!
