On Wed, 3 Sep 2008 14:54:17 -0400, Michael Black wrote:

On Wed, 3 Sep 2008, raypsi wrote:

Hey Gary,

Rocks aren't cheap he http://www.icmfg.com/thruhole_crystals.html
Maybe in 9 land they pave the streets with gold.
Personally I'd go with a programmable divider or PLL.

Maybe you like retro, then I'd get some old rocks the ones
you can take apart and grind them down to git's the freq's you need.

And you can't grind them unless they are quite close to the desired
frequency. Grinding by hand will be too uneven, so the crystal will
stop working if you try to grind it more than a tiny bit.

My personal experience is an FT-243 crystal's frequency can be
increased by several hundred kilohertz through grinding. A more
abrasive media is needed for the slurry than scouring powder can
provide. Permatex 34A valve grinding compound works FB. Most of my 80M
rocks (26 between 3.5 & 3.6 MHz) were originally cut for 3237 kHz.
Many of my 40M crystals were moved several hundred kHz as well.

The key to grinding is not to try doing too much at once. Let the
abrasive do the cutting, no downward pressure is need from the
fingers..

It also relies on a big stock of crystals spread around so you can
find one sufficiently close enough, something that did seem possible
in the years after WWII, but after all this time attrition may have
reduced the stock considerably.

There are still a lot of them out there and they can be most
inexpensive if the actual frequency isn't too important.

73 de n4jvp