I think you'll find at least two or three crystals in
every two-way radio made today, as the reference
oscillator of the synthesizer, the microprocessor
clock generator, and the 2nd oscillator for the
receiver. Not much else you can use in an oscillator
circuit that affords as much stability as a good old
crystal, even if it is inside an oscillator module.
Bob M.
======
--- MCH <[EMAIL PROTECTED]> wrote:
> Regardless of how many modern radios use temperature
> stabilization, that
> does nothing to diminish its effectiveness at
> keeping the frequency
> stable and eliminating the need for temperature
> compensation.
>
> Few rigs today use crystals for the operating
> frequency. Does that mean
> crystals are bad?
>
> Joe M.
>
> Bob M. wrote:
> >
> > 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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