Xtal grinding

[Mike Morris]

At 06:17 AM 01/15/2000 , you wrote:
>Hello to everyone on the list.
>
>I need some help. Does anyone remember the material used to make a
>grinding compound for grinding crystals? I have some xtal's I'm trying
>to rubber in to the AM window on 75M, etc.
>
>Thanks   Walt   W1ATV

I seem to recall an article on crystal grinding in one of the
ARRL pubs (Amateur's Handbook?) in the late 50s/early 60s.

I never did any for HF, but I've moved a bunch of FT-243's in
the 6mhz and 8mhz range for old Motorola 2m radios,  for two
Link Corp VHF monitor receivers, and for a couple of GE
Progress Lines.

I used Bon Ami on a plate of glass (a piece of a louvered
window) in a figure-8 pattern.  Use one finger, gently, and
wash well and let dry overnight (or use a hair dryer on low)
before checking the freq.
As the crystal blank dries it changes reflectivity due to
the moisture.  Use the hair dryer for 3x the time it takes
for the reflectivity change to be complete before measuring.
I moved crystals as much as 600khz, but was never able to get
more than that.

Try not to round off the edges - it makes the crystal hard
to start.  I did that with three, and was able to salvage two
by holding the blank at right angles to the glass (I used a
carpenters's square because I had one handy, it may not have
been required) between thumb and first finger and ground gently.

Work slowly.  Measure often until you develop a feel for how
many Khz per hour you can move things.  Every time I tried to
rush things I killed a crystal.

Over six months in the early 70s I ground crystals for 146.82
and 146.70, and for 146.22/82, 146.01/61 and 146.46/46.

I also ground a set for a 146.10/70 set for a 1960's Motorola
A-strip base which was in service until a few years ago when
I retired the Model 15 Teletype.  The tone generator was a
regular Moto tone-burst encoder - a 6C4-based audio oscillator
strapped for continuous duty, with a keyboard-driven reed relay
adding a capacitor to shift the tone.

Mike

Sponsored by the City of Tempe 

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