Carl Hoffmeyer wrote:

Hi Pankaj,

The last time I did crystal grinding (which is what you are
*really* doing, I used a very flat piece of 1/2" plate glass
for the surface. The agent (grinding compound) was jeweler's
rouge and a bit of distilled water as a vehicle.

We held the crystal with our fingers (in Platex gloves) and
took a few very measured circular passes.

When I did it I was told to make those passes in a "Figure eight" movement.

We counted the revs.
A wonderful ham we knew (Mr. Irvine), designed and built a very
neat tester/oscillator to judge the results before sticking the
futtering FT-243 crystal holder all back together.

It consisted of wide respsonse oscillator using a computer
switching transistor (2N706 or thereabouts), a *very* thin
copper wire soldered to a small brass flathead woodscrew. The top
of the screw was polished down and could be lifted and placed
anywhere on the surface of the rock ... errh ... crystal.

The crystal sat on a polished brass flat (an old brass gear).
The gear and the wood screw served as the two contacts for
the rock.

I had pretty good luck raising the fundamental frequencies of some WWII
"war surplus" FT-243 crystals up into the 40 meter ham band circa 1950.

If I overshot a and raised the frequency a bit too much, I used to lower
it a little by rubbing soft solder (cold) onto the center of the crystal
blank, adding a little mass back onto it. Those crystals were the types
held between two metal plates formed to grab them at their four corners.

I've still got about twenty of those FT-243 crystals in a box somewhere.
I guess they'll stay where they are until my survivors toss them out,
along with a couple of stacks of QSL cards from those halcion days.



snipped

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."