[ARC5] OT: Hally Instability

[Arden Allen]

> .....Has anyone ever tried to determine the source
of this mechanical instability?  Cheap tuning cap?
LO coils mounted by their wires on the band switch? .....

All of the above, I'd say.  Think of the chassis as a kettle drum skin.  As 
it vibrates it changes planarity.  The parts mounted on the chassis move to 
and fro with respect to each other.  As you go up in frequency the resonant 
frequency of the tuned circuit is more heavily dependent on contributed 
stray capacitance which varies with vibration causing FM'ing of the LO. 
Take a sturdy non conductive probe like a wooden cooking spoon handle and 
flex the chassis at various points to see how much FM'ing you get.

An analogy is you can't make a silk purse out of a pig's ear.

Arden Allen
KB6NAX

He who is cruel to animals becomes
hard also in his dealings with men.
We can judge the heart of a man by
his treatment of animals.
—Immanuel Kant