B
bitrex
Guest
Here\'s a paper on the theory of crystal ovens:
<http://www.karlquist.com/oven.pdf>
There\'s a lot more to it than just slapping a crystal & heater in a
metal box and calling it a day! There are probably some pathologically
bad geometries even a really fast control loop can never stabilize very
well.
The part about the outer can acting like a Faraday shield is
interesting, shunting ambient gradients around the core. Does anyone
know how they make the negative space look like a linear tehrmal
resistance over a wide range? There\'s some kind of insulating foam in
there, is main heat thermal transfer radiative or conduction?
I picked up an otherwise really nice HP 5334b frequency counter with
both the 1.3 GHz input and OCXO options for a song. Unfortunately
there\'s a fault somewhere inside the OCXO module and it outputs about
1.8 MHz instead of 10...seems to be maybe a bad cap somewhere around the
Colpitts section and the crystal and heater sections are OK.
The heater transistors screws to the internal mass have to be re-torqued
to spec if you mess with them, I didn\'t mess with \'em.
<http://www.karlquist.com/oven.pdf>
There\'s a lot more to it than just slapping a crystal & heater in a
metal box and calling it a day! There are probably some pathologically
bad geometries even a really fast control loop can never stabilize very
well.
The part about the outer can acting like a Faraday shield is
interesting, shunting ambient gradients around the core. Does anyone
know how they make the negative space look like a linear tehrmal
resistance over a wide range? There\'s some kind of insulating foam in
there, is main heat thermal transfer radiative or conduction?
I picked up an otherwise really nice HP 5334b frequency counter with
both the 1.3 GHz input and OCXO options for a song. Unfortunately
there\'s a fault somewhere inside the OCXO module and it outputs about
1.8 MHz instead of 10...seems to be maybe a bad cap somewhere around the
Colpitts section and the crystal and heater sections are OK.
The heater transistors screws to the internal mass have to be re-torqued
to spec if you mess with them, I didn\'t mess with \'em.