[Boatanchors] Crystal grinding question

[Bob Bethman]

Jack,

The quartz crystal is going to be essentially the same.

However, the difference is most likely due to the cut of the crystal.

Crystals were cut at different angles at different times.  One well known cut was the "AT".  A bit of digging would tell the different designations.  Each one would have different characteristics that would cause differences in movement when grinding them.

Regards, Bob - N0DGN

-----Original Message-----
From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Jack Antonio
Sent: Saturday, August 13, 2016 4:15 PM
To: Boatanchors <boatanchors at mailman.qth.net>
Subject: [Boatanchors] Crystal grinding question

I just tried to grind a pair of crystals to a needed frequency in the

75 meter band.  One was 2kc low, even though it could be an original

military crystal, it probably is most likely a JAN or Texas crystal, I

would say 50+ years old.


The other was 3 kc low, and was made by CW Crystal, which I'm guessing

dated from the mid 90s, so about 20 years old.


Both of these are FT-243 holders.


The old crystal moved up nicely. It took about 200 figure 8 passes with Bon-Ami

and arrived within 100 cycles. One session of 100, next of 50, and two touch

up passes.


The newer one only moved 1 kc. The first pass of 100 swipes netted a 500 cycle

change, with each following session moving the frequency less and less. 
After a

total of 500 passes, with renewing the Bon Ami, the frequency had only moved 1kc.


The two blanks were different, the old one was square, or very close to 
square,

the newer one rectangular.


So, the question is, is new quartz harder than old quartz? Or could 
there be some

other mechanism at play here? Going to start looking for some Whink.


Jack Antonio WA7DIA/4