[R-390] 200kc crystals

[Tim Shoppa]

N4BUQ asks:

> Is it possible to disassemble an HC-6 crystal and grind it to a different frequency?

In general, yes. Grinding or etching to shift a crystal up a
few kc is not so bad.

> Since 200kc crystals are getting pretty rare, I was
> wondering if a 455kc could be ground to 200kc.  More
> trouble than it's worth?

Not gonna happen that way. You're not talking about a
percent or two shift upwards, you're talking about
a complete shift downward by more than an octave.

I'm not an expert in the 200kc crystal cans, but below
a frequency in the kc range the crystals are done as
tuning forks rather than as rectangles.

ART-13 crystal calibrators use 200kc crystals, if you've
got one of them lying about for parts.

Some folks use 100kc crystals in their R-390A's, and
get 50kc calibration marks with a small modification to
the stuff around the 5814A's on the RF deck.

Tim.