[TenTec] noise in receivers

[Dr. Gerald N. Johnson, P.E.]

Any oscillator with PLL is going to be noisier. Any oscillator mixed
with signal is going to show more reciprocal mixing with a noisier
oscillator. The 830's PLL offsets is fairly clean because the loop
bandwidth is high. The design of each VCO has a lot to do with the noise
spectrum of the oscillator. Using more bands in the VCO helps cut down
on phase noise because it reduces the sensitivity of that VCO to noise
on the control line, and allows the VCO to have better stability...
Phase noise is a measure of instability of the oscillator. So any
oscillator physical construction (even the infamous kenwood goop) that
is more mechanically stable often helps phase noise.

The PLL in the Omni V and VI is at VHF then divided down to the 5 MHz
region for the mixing with incoming signals. Division narrows the phase
noise. I'll not soon find out with my own radios if they are as good as
the Corsair II because of that CW mode problem I grumble about
regularly, though I do know of some that I could take an IMD test set to
and make some measurements soon as I finish building it.

Wide range PLLs like would be used in the Paragon for general coverage,
tend to be noisier because the raw VCO is far less stable.

The VFO 230 and 830 should have the worst of both worlds.

73, Jerry, K0CQ

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