Thanks to both Bill and Harry.

I'm trying to vary the resonant frequency of a loop with an air
variable. The loop impedance is under 1 ohm, so it needs a step up
transformer anyway, and toroids are commonly used.

Since a 1000 pf varaible is much harder to get than a 10 pF, I was
pleased to learn that I could multiply the effective value by
multiplication of the actaul value times the square of the turns
ratio.

It makes the job much easier, even if the Q of the loop suffers some.

Thanks to you both,

T