[Jon_G4MDC]

I thought I would take a look at the manual - never having owned one of these receivers.
They certainly describe the working of it in the wrong way.

"The LOCK lamp lights up when the synthesised heterodyne oscillator is unlocked."

I reckon that's a copy/paste error from the manual writing department. They probably weren't fed enough information (very common) - work it out for yourselves. Synthesised - nope. Unlocked - nope. Off tune - well yes.

Just hoping to keep the thread alive until the OP can come back and tell us some more. It's a set I thought about buying, back in the day, but I never did.
Maybe I need one now, just to see if they are any good.

I have been thinking about how it would work with the HF(Bandset) LO phase noise vis-a-vis a synthesiser. Might it cancel through the different mixing routes?
As there are two different BW filters in the mixing paths there are 2 different delays - maybe this gets rather off topic.