Thanks Grump...gonna save that for my files but I think I need to
clarify my question. One cap only...not one across the tank and another
on the tap although thats an interesting idea. Maybe this schematic
will help.

http://www.antiqueradios.org/gazette/pix/sw3-1sch.jpg

-Bill



Grumpy The Mule wrote:
Howdy,

I'm guessing that it can be solved like this...
Consider the autotransformer action of the tapped inductor.
Then divide the tap capacitor (C2) value by the square of the
turns ratio (N) before adding it to the primary capacitance
of the parallel tuned circuit (C1.)

F=2Pi*sqrt(L(C1+C2/N^2))

I found a rigorous solution in chapter 8 of Alternating
Current Circuits by K.Y. Tang but it's too messy to type.


73,
Grumpy



exray wrote in :

Hi,
Can somebody walk me thru the calculation of an LC circuit where the
capacitor is tapped down on the coil? I see this often done for
bandspreading purposes.

Tnx,
Bill WX4A