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Thread: What Test Gear to measure xtal frequency to 1Hz
www.piclist.com/techref/timers.htm?key=xtal
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face BY : Jim email (remove spam text)



.
>  "The original TXCOs were really a challenge since
>   you had to use analog circuitry to match the
>   tempco of the crystal and other circuitry"
.
Motorola mastered this technique late in their
"Motrac" series ("Motorola Transistor Research Line"
of 2-way FM commercial radios) - with the last ovenized
crystals used about 1965. All the newer product utilized
a technique in the form of little modules known as
"channel elements" versus discrete "crystals" placed
in small ovens.

To build these solid-state "channel elements" it was a
matter of characterizing each xtal and determining it's
"curve" (see Peter's postings) and selecting the
correct valued compensation cap to placed in series
with thermistors (with various characteristics) along
with other ceramic caps that had also known variation
over temperature ...

I've uesd the PTC thermistor myself - to keep a 10.24 MHz
ref osc on frequency over temperature in an automotive
install on a VHF Engineering 2-Meter synthesizer that gave
"frequency agility" to a 1965 "E"-series Motorola Motrac
in the mid-70's (predating the compact, Japanese synthesized
radios by a few years!) ...

RF Jim



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Subject (change) What Test Gear to measure xtal frequency to 1Hz

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