I remember one of those watering hole crystals was 7.040 MHz.... I
still have mine, an FT243 type. It came from a box of dozens at the
same freq. Worked fine on 21.120.
Several of us local hams (Glendale, CA., early 70s) used the same method
of graphite on the side to slidea couiple kHz. Right away after, the
FCC lifted the ban on VFOs. :)
73,
matt W6NIA
On 1/21/2017 11:09 AM, Bill Johnson wrote:
Ron, I used a wet stone that was flat and with spit. Lots of work to get to
the desired frequency. We had a bunch of surplus Army surplus frequency
oscillators that provided us with XTALs most were out of band so it was a
chore, but cheap, to move the frequency.
73,
Bill
K9YEQ
-----Original Message-----
A crystal oscillator might "drift" a few tens of Hz at H.F. on its fundamental
frequency but in all the dozens of xtal controlled transmitters I've built and used over
the years, nothing greater than that.
There were some circuits designed to "pull" the frequency of a crystal slightly
- maybe a few kHz - but they did tend to be unstable. Pulled too far, the crystal
oscillator would stop being controlled by the crystal at all and simply become a
free-running oscillator.
Many novices used "surplus" crystals from military gear and it was common to
find several stations on the same frequency when the band was open. So we tinkered with
ways to move the crystal frequency slightly by rubbing solder or pencil 'lead' (graphite)
on it but one could only go so far or the crystal would stop oscillating.
73, Ron AC7AC
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Always store beer in a dark place. - R. Heinlein
Matt Zilmer, W6NIA
[Shiraz]
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