Use Guitar Tuner to Match Crystals

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From: James R. Duffey (ji3m@maxwell.com)
Date: Thu May 29 1997 - 09:43:29 EDT


Tim - You don't need to have perfect pitch to recognize when the crystals
you are measuring by beating an oscillator with the unknown and a receiver
BFO together. Use a guitar tuner. Set the switch to a comfortable, probably
A (440) or higher note and tune the receiver with the BFO on so that the
needle on the tuner indicates it is in "tune". Record the frequency on your
receiver. Repeat for the rest of your crystals. Use the ones that are
closest together. You may wish to record the S-meter reading as some sort
of indication of activity or Q which may also be useful to match if you
have enough crystals. This method insures that the zero beat is always at
the same frequency.

I use my daughter's guitar tuner, but you can purchase them at most music
stores for around $15-$20. They are useful devices around the shack. I have
used it to measure the doppler shift on the mode A birds as well as
insuring that I am zero beat with the last caller during the fox pileups
and in setting my transmit/receive offset.

Good Luck. - Duffey KK6MC/5

James R. Duffey
Principal Scientist
Maxwell Technologies Incorporated/Albuquerque Division
Suite 300
2501 Yale Blvd SE
Albuquqerque, NM 87106

(505) 764-3143
(505) 843-7995 (FAX)


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