The first fix might be to put a non conductive insulator
over the crystal (xtal). A foam pad or rubber sheeting is
sometimes used by various mfgrs. Just floating a crystal
to relative exposed cabinet/box air is not so great if
the air temp changes more than a small amount.
Second item which might help would be to seal the box
and possibly insulate it from larger thermal changes as
mentioned above.
If things get really out of hand, you could find/buy a
typical Ovenair Crystal unit from various places (like
Hamtronics) along with the proper Ovenair type crystal.
I would not put a standard room temp crystal in an Oven
air unit, nor would I try the xtal heater (resistor) trick
on a xtal not spec for operation in a heated loop/oven
circuit. Chances are it's not going to be anywhere close
to the desired frequency when you heat it to normal xtal
oven temps...
Keeping in mind the Ovenair unit draws a lot a bit of
serious current in operation... ie not so great for solar
only radio sites.
Also note the crystal pins often plug into a tin plated
holder. It might be prudent to swap the crystal holder pins
for something better. I use older gold plated transistor
sockets that can be found surplus or removed from vintage
salvage. The cheaper xtal socket/pin metal doesn't help
much as well as the xtal floating in air.... and the exposure
to mechanical vibration.
I have seen & heard of numerous examples where you could
modulate a transmitter with modest hits to the outside
equipment case.
A most funny college example was a friend actually using
a B&K VFO for Two-Meter operation. Sitting on a firm thin
table you could actually yell close to the table surface
and hear the audio on the air.
Your results will probably vary...
cheers,
skipp
> [EMAIL PROTECTED] wrote:
>
> At 5/23/2006 07:20, you wrote:
> > >
> >One other thing you might try - tape a 100 ohm 1 watt resistor to the
> >side of the crystal and put 12 VDC across it. Not a pretty sight, and
>
> If you're going to heat the crystal, might as well use something
that will
> keep it at a more or less stable temperature: a 50 ohms 50 degree C PTC
> thermistor. Digikey has them for $1.68 each (manufacturer part #
> RL3006-50-50-25-PTO). Desolder one of the leads & solder the disk
directly
> onto one side of the crystal, ground the crystal case & apply a
regulated
> voltage to the other side.
>
> Bob NO6B
>
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