Joe, As you know crystals are not bad. And when one puts on a repeater that stays sometimes for couple decades on the same freq crystals are fine.
Also as you know crystals take time to get. Having synth repeaters/rigs allows even the commerial guy to keep a few radios for spares allowing to quickly program up for a customer in the event of a failure. This is where I see synth has a deffinite advantage. Out of the box, 10 minutes later ready for service. As for repeaters synths did have the problem of more noise, but engineering solved this in repeaters. Another reason why not to use 2 mobiles or HTs for a repeater. There are other reasons. 73, ron, n9ee/r >From: MCH <[EMAIL PROTECTED]> >Date: 2007/07/12 Thu PM 12:26:42 CDT >To: [email protected] >Subject: Re: [Repeater-Builder] Re: crystal/channel element compensation.. > >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. >> > ... >> >> >> __________________________________________________________ >> Be a better Globetrotter. Get better travel answers from someone who knows. >> Yahoo! Answers - Check it out. >> http://answers.yahoo.com/dir/?link=list&sid=396545469 >> >> >> Yahoo! Groups Links >> >> >> > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
