On 2010-01-28, axolotl wrote:
On 1/27/2010 5:00 PM, DoN. Nichols wrote:

Interesting. I remember building an array of oscillators using
CMOS gates as driving elements, and a high valued resistor and a trimmer
capacitor as tuning elements. The major problem was that it was not
stable with temperature. I wonder whether using low TC mica capacitors
and hand-drawn resistors would produce something more stable. (I didn't
use trimmer resistors because I had a lot of the trimmer capacitors from
a surplus deal, but not enough trimmer resistors -- and that many would
have been *expensive*. :-)

Back when I used to do this sort of thing, the standard method was to
use a varistor with a TC inverse to that of the capacitor. If you wanted
an LC oscillator, there was a ferrite core material that had a
complementary TC to polystyrene caps.

Interesting approaches. I think that I might have done well to
simply set up a divider chain from a crystal oscillator. All the target
frequencies were in the audio range, and not particularly sensitive to
harmonics, so the square-wave output would be easy enough to use.

Enjoy,
DoN.

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