>Greater stability can be achieved using more sophisticated
temperature control, including keeping the area warm even when
the radio is off, or using a crystal oven
...or simply leaving the power on continuously.
I previously worked at HP where we sometimes used Peltier devices
for oscillator temperature stability
in high precision digital voltmeters (A/D techniques
convert V to F so oscillator stability is important
for ppm range voltage accuracy). You might be able
to mount one of these directly to the crystal can.
>however, for most purposes, this should give the kind of
stability needed to prevent being 20 Hz high or low on a net
(I heard several stations off by at least that much on the
Ten-Tec net today, a couple of them using Orions), which is
noticeable on SSB.
...which begs another question. If you can hear that
you are off frequency by 20 Hz, why is ppm accuracy even
necessary in the first place? ;-)
73, Bill W4ZV
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