> Have you tried varying the RC oscillator Vdd from say 4.5V
> to 5.0V or 4.0V to 5.0V instead of varying the resistance?

Looking at the charts I don't think that's going to give me the
frequency range I need. A good thought though, maybe I can
use it in some way

> Alternatively, you could make a current source controlled by
> linear potentiometer to feed the oscillator, I think that would
> be very linear

I'm not quite sure what you mean. Another alternative could
be a linear VCO. I have a good one for audio which is 1V per
octave, perhaps I can modify it to run at the higher frequencies
and use ECIO

Thanks
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