Which is why I specifically said "for the operating frequency" - to eliminate the argument you just made.
My point was that crystals are still fine for a repeater - as is temperature stabilization - even though modern radios may not use either. Sometimes, newer is not better. Joe M. Bob M. wrote: > > 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. > > > ____________________________________________________________________________________Ready > for the edge of your seat? > Check out tonight's top picks on Yahoo! TV. > http://tv.yahoo.com/ > > > Yahoo! Groups Links > > >
