I don't consider the Omni V/VI in the same class as the Corsairs.
Best I can detect, the early Omni (A,D,C) used a double gate mosfet as
RF stage. This can have usable dynamic range but not the best.
The Corsair II uses a bipolar transistor with transformer feedback. The
circuit that Ulrich Rohde's book on receiver design concludes is the
best available RF stage for dynamic range.
All Ten Tec before the Omni V use the same PTO and crystal mixer in the
LO injection circuit. There have been some variations in the side of the
injection necessary to prevent bad transmit spurs on some WARC bands.
I don't know about the Omni VI, but the Omni V uses 4 JFETs in grounded
gate with independent source bias resistors for the RF stage. I have to
do some tests of the circuit independent of the other variations in the
radio to decide whether it is as good for dynamic range as the Corsair's
RF stage. The Omni V/VI use a synthesized VFO which probably means its
not quite as clean for phase noise as the PTO in earlier radios. The
design seems good, but I have my reservations. The synthesized VFO is
mixed for most bands just like the PTOs.
There are those who believe the differences in single/double conversion
(and it takes the double conversion receiver to allow for IF SHIFT) make
the single conversion receivers quieter and more sensitive to weak
signals. So those single conversion receivers would make a different
design. Mixers do add noise so there may be merit to the arguments,
though I've not yet tested the theory.
That would place the Triton/540/544 in a separate class from the Omni
A/D/C.
73, Jerry, K0CQ
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