[time-nuts] Improving the stability of crystal oscillators

[John Ackermann N8UR]

SAIDJACK at aol.com said the following on 10/10/2007 02:17 PM:
> In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, jra at febo.com  
> writes:
> 
>> We  first built a small proportional heater circuit that we could shove
>> in  next to the crystal, and that worked OK.  We finally found a  source
>> for thermistors spot welded to a spring clip that would mount  snugly
>> directly to the crystal case.  With 12 volts applied, these  heated the
>> crystals very nicely.  With the heaters, we were able  to keep the
>> systems running year round with about 1/10 the service  calls.
> 
> Hi John,
>  
> interesting anecdote!
>  
> Would you know if the thermistors are still available? Who made  them?

We bought them as a replacement part from Yaesu USA.  This data is 10
years or more old, but here you go:

Part Name	Yaesu Part Number	Murata Part Number
Posistor	G9090019		PTH507A01BG330N020

They used to be about $7.00 each.  Yaesu's parts-order phone number at
the time was (800) 255-9237.  I'm not sure if there's another source for
the Murata part; back then, we couldn't find one.

Amazingly, I still have a web page documenting all that we learned about
those cursed radios, including the schematic of our original homebrew
heater design: http://www.febo.com/hamdocs/d4art.html.  The quality of
the heater schematic isn't very good, but it's all I have.

John