vco7c thermal results

[jorgen.bergfors at idg.se]

>These are not the kinds of tests you do no a non-tempcomped
>circuit....obtusely. I wonder how your tempco would react to such extremes.
>Anybody want to hurt your vco (compensation of your choice) a little for a
>comparison? BTW when I said "then after a little minor drifting" maybe
>+-5hz .It was useable at the initial frequency within 60secs of being
>thermally slammed. I though that was pretty good. 

>-tg 

What I found out is that if you heat only selected components the results will be worse. In a real life situation the entire VCO board will usually be rather evenly heated, so I think it is pointless to heat or cool off just the expo converter. I tried putting a spotlight close to the board, to heat it. That caused more drift than the box test, both with and without tempco resistor.
Next I'm going to try connecting a 3000 ppm/C and a 3900 ppm/C tempco resistor in series or parallell. Currently I'm only using a 3000 ppm/C tempco, which undercompensate slightly. Using two tempcos is not a problem, as the SMD ones are so cheap.

/Jörgen