David KE4FPS made a comment about the Corsair II's reputation as a fine hf
radio. I've had mine for about a year (bought used, of course), with the full
filter complement. It replaced a now-retired Kenwood TS-430, and the
difference in performance is astounding. Whereas the 430 is a hissy,
phase-noise plagued all-digital "wonderbox" that actually gave me headaches in
trying to dig very weak signals out of strong ones in crowded 20 meter
conditions, the Corsair II delivers extremely clear, clean audio. In fact, I
specifically bought this last-generation of PTO-tuned analog hf radio (the
Corsair II) just to get away from the phase noise limitations of that stupid
ricebox.
My operating habits tend towards long-term copy of very weak signals amidst
very strong ones. The Corsair's cascaded filters, quiet LO chain and clean
audio makes a huge difference. It's passband tuning, notch filter (which is
*inside* the AGC loop where it belongs), and bandpass filter also contribute
to successful copy impossible with the synthesized rig.
I've done careful measurements on the Corsair receiver vs the TS-430 and find
that on the 430 a 2-5 uV CW signal 20 kHz away from the frequency you're
trying to hear will actually increase the noise level (that's reciprocal
mixing, or phase noise). The Corsair has *40 dB* better performance; an
extremely quiet receiver which translates to much better weak signal
performance under crowded band conditions. No wonder I don't get headaches
anymore.
I guess the latest Japanese synthesized whiz-bang sets probably do better than
the TS-430, but I bet they still don't beat the Corsair II.
-- Rick WA6NCX
remler@ll.mit.edu
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