[NLRS] Simple temp controller for crystal oscillator

[Doug Reed]

<http://pensacolasnapper.blogspot.com/2011/03/temperature-controllers-for-qrss-part-2.html>

This link has a fairly simple circuit for temperature control that can
be added to any crystal or crystal oscillator. It certainly isn't as
accurate as the DB6NT temp control but it is probably a bit more
accurate than using a simple PTC resistor for temp control. It is a
simple 4 part circuit and it probably will do a pretty good job. You
might want to save a copy of the article for future reference.

One of the other blogs on the same page mentions some tests he ran
using a crystal can oscillator and putting it in a small foam block.
The foam, even without a heater, stabilized the oscillator quite a
bit. This would have possible application for making a cheap
weak-signal source for the microwave bands.

73, Doug Reed, N0NAS.