Duane,
Thanks for the reply. I went back and reviewed your original posting.
http://lists.contesting.com/archives//html/TenTec/2004-12/msg00116.html
In the case of the Pegasus and its design similar siblings I
often thought that the 45 MHz IF is the best place to apply
this idea. Unfortunately in the case of the QSD that high of
a frequency is a bit of a challenge to get to. Although I
think decent results could also be had by applying the QSD to
the 455 kHz IF of the Pegasus instead. The other limitation
of using a radio like the Pegasus or its sibs for such work
is that the 45 MHz IF roofing filter will limit any
QSD/external DSP IF to ~15 kHz of bandwidth. To me that is
too restrictive given the increasingly common use of 96 kHz
bandwidth in the SDR radio programs like Rocky, PowerSDR, and
Winrad. I suppose if you only want a narrow bandwidth IF then
that is not an issue (that's exactly what I had with the CII
experiments I did). I suppose with some creative design you
could actually do both bandwidths, narrow for optimal DR
performance and wide for panadapter purposes.
I hadn't really looked at the Pegasus mixing scheme, which kind of messes up
what I was thinking about. I was really thinking about using some frequency
in the Pegasus (I forgot about the 45 MHz) as the VFO for the QSD. That
would require a frequency near the intended tuning range, which probably
doesn't exist in the Pegasus.
Also in the case of the Pegasus and its sibs the prospect of
TX with a QSE (or any other baseband to RF mixer scheme) may
be a bit challenging to implement, not likely to be a
"restorable" mod to make. For some reason I can't ever bring
myself to making mods of this level to a radio that can't be
undone.
I figured I'd just use the Pegasus' transmitter.
And finally I do know that there are some that are taking the
12 kHz IF out of the RX 320(D) and feeding it directly into
Winrad. This works because Winrad does not need I/Q inputs to
work. This was discussed within this last week on the RX 320
group on Yahoo.
I have modified both my Pegasus and my RX320 to bring out the 12 kHz IF and
have decoded that with a computer, but I was thinking that a QSD mixer might
work better, plus you would be able to get twice the bandwidth if you have
both I and Q - though I hadn't thought about the roofing filter.
73,
Mark
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