On 2/15/08 10:26 AM, in article ,
"Jeffrey D Angus" wrote:

John Byrns ) writes:
I'm still wondering why these are in tube type cases. It almost suggest
they are better than average crystals, and makes me wonder if they actually
have some sort of heater built in.

They're just a bit better than the tall HC/6-U crystal holder. And less
prone to enviromental issues than the FT-243 type holders.

The "tube" versions usually don't have a heater built in.

So the question is, what are these good for, can they be converted into
a useful project of any sort?

With the availability of crystal oscillator assemblies having better
than 10^-12 stability and and accuracy, there's not much you can use
one of these old crystals for.

A crystal oscillator will not achieve 10^-12 on its own. 10^-12 is the
stability of a Stratum II atomic clock.

That being said, they're fun to set up
with a square wave output so you can use them as a "calibrator" for
a SW radio at the 100 KHz markings.

Michael Black wrote:
I actually have a 1MHz crystal that does have a heater element. Big metal
thing, though I can't remember if there's a thermostat there. It's from
an AM broadcast band transmitter.

Michael VE2BVW

That is a typical oven type which is used as a reference oscillator.
The ovens came in two separate versions, for the most part, they had
the oven and control built in. A few of them just had a heating element
and temperature probe.

Jeff