"Highland Ham" wrote in message
...
Using polystyrene caps and with the VFO not having any buffer stage the
device fed by a 9v PP battery drifts not more than 20 Herz in 30
minutes.
----------

What kind of battery is a 9v PP battery? And, it would likely be helpful
to know what the Inductor is that the negative temperature coefficient of
the poly cap is compensating for. Is that drift specification for the
first 30 minutes after turn on or after the oscillator has been on for a
couple of days?
-----------
A 9v PP battery is a standard battery pack , alkaline /NiCad / NiMH as
used in all sorts of consumer electronics incl battery operated smoke
alarm devices. Dimensions :45x25x17 mm. Available all over the world.
The battery is 'velcro-ed' to empty space on the board
I did not use dedicated neg temp coeff components ,but used 4 recycled
polystyrene caps from the junk box.

And I assume that the PP means Peak to Peak. I'll acknowledge that a battery
has a peak Voltage, in this case, something close to 9 Volts. I doubt it
could be rated as Peak to Peak which would imply at least a couple of the
things wired back to back and providing around 18 Volts. (Peak to Peak
speaking of course, not Push Pull, cancelling even harmonics, or even
Push-Push, cancelling odd ones.)

The polys have a generally acknowledged negative temperature coefficient and
as such must be correcting for something. The inductor is an air wound
solenoid, wound on a toroid or perhaps a (for the frequency range spec'd)
quite long piece of coaxial cable?

If you observed 20 Hz of drift over a half hour, after a 20 minute warm up,
I would be inclined to ask as to the ambient temperature variation during
that 30 minute exercise.

W4ZCB
NOT linuxed, have enough trouble with Bill Gates's products.