[Amps] Pi-L values

[Tom W8JI]

Ken,

You are on the right track.

> The Sunair manual states "The tuning and loading
> capacitors, C20 and C25 are mechanically ganged
> and motor driven ... the ratio of C20 to C25 should
> be approx 2.5.

Then that is what it should be. It is quite possible to have 
that value in a Pi-L.

>>I'd look at stray C on the plate tuning cap as being
> a
> contributor. One would think they compensated with
> some
> fixed C at another appropriate spot in the tank, like
> across
> the "loading" capacitor.>
>
> Yes - there is a 50 pFd cap in parallel with the
> loading cap.

Then they allowed for the stray C in their design, which is 
what we should expect. I'd expect them to know more about 
their design than any of us.

> "The nominal desired plate impedance is 1900 ohms
> with zero phase angle..... the junction is the midpoint
> and is near 100 ohms.   The midpoint impedance
> can be measured and is an indication that the ratio
> of C25 to C20 is the proper value."

The problem is measuring that impedance without a high input 
impedance vector impedance meter of some type. You want to 
be able to measure that value without perturbing the system.

Are the inductors ganged also, or are they separate drives?

73 Tom