The 5.0-5.5 MHz VFO and the band selection crystal oscillators in the
Omni VI are both locked to the reference oscillator on the logic board.
So if the reference oscillator is on the right frequency those two
oscillators will also be (unless something is really wrong). The BFO
crystal oscillators are not locked to the reference oscillator. So the
frequency readout accuracy depends on the accuracy of the reference
oscillator AND the BFO. There are two crystals and five adustments in
the BFO. Depending on what mode the radio is operating in, one crystal
and one or more variable capacitors effect the BFO frequency. Diodes
switch in different variable capacitors in different modes, to "pull"
the crystal slightly.
Some radios have ALL of their oscillators locked to a single reference,
and if that one reference is on the right frequency, everything else
will be and the frequency readout will be too. Some radios have higher
phase noise too.
DE N6KB
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