I beg to differ.
Few MODERN commercial rigs (built since the 1980s) use
heaters, but prior to the Micor, almost all of the
vacuum-tube two-way radio sets definitely used crystal
heaters. I have the burn marks on my fingers to prove
it. The temp was usually around 85C and the units
operated from 6 or 12 volts which was always available
as a filament voltage. The GE units could hold two
crystals and used an 8-pin octal-style plug-in module.
The Motorola units could hold one crystal and used a
4-pin rectangular module. When ordering crystals from
ICM, one could specify whether the unit was to be
heated or not, and if it required large pins (to plug
directly into the radio's socket) or small pins (to
plug into the socket inside the heater). I'm not sure
you could call these "ovens" as they used a mechanical
thermal switch to control the temperature and the
crystals were firmly mounted inside the units.
Crystal ovens were very common in older (tube-era)
broadcasting equipment, however in the more modern
synthesized units they might have a TXCO or even an
OXCO for a reference oscillator (depending on how
cheap the manufacturer was). AM broadcast stations
rarely use ovens these days; the crystals are stable
enough to keep the carrier within +/- 10 Hz (about 10
ppm) which is better than the FCC requirement.
Bob M.
======
--- Ron Wright <[EMAIL PROTECTED]> wrote:
> Few commerical rigs use a heater to stablize the
> frequency. Some see it in applications such as
> broadcasting where very tight, much tighter than
> commerical, frequency is required.
> ...
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