I agree with Jerry in that Tritons are in a different class than the early
Omnis, but not because of the conversion. They are both 9 Mhz single
conversion, with the later Omnis having provisions for crystal cw filters.
My memory is that the double conversion did not show up until the Corsairs
which used 9 Mhz and 6.3 Mhz in part to achieve the passband tuning. The
double conversion probably also help image elimination to some degree, but it
does add some white noise.
Left out of the discussion so far is the 580 Delta which is single
conversion, but with a 6.3 Mhz IF. I assume that 6.3 was chosen to eliminate
the 18 Mhz spur problem inherent in the old Omni due to the mixing scheme.
The Delta PTO is slightly different in frequency coverage and I believe it
tunes backwards compared to the rest of the PTOs.
The Argosy series are kind of cut rate Omnis with a 9 Mhz IF, no VOX , and
with only 30 meters for WARC coverage. That is about as good as I can do
off the top of my head and will leave it to others to discuss the later rigs
with upconversion, etc.
Walt
WA4VEC
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