:Cecil,

I will start a little long as this is a peimo piece of 2" dia brass.
According to swr-freq by R. J. Edwards, the 2" dia sleave is about 50
ohms
for the 1/4 wave. 146 mhz, 51.1 ohms, jXin 0.0 .

My thaught is with the 1"mast inside of the sleave (insulated and
centered only connected at the top) what does the added capacitance do
to the sleave lenght?

And RFS does not have the old cutting charts for the Phelps Dodge PD83,
I tried that.

"Will" wrote:

How do you figure the lower "coaxial sleave" dimentions.
Cecil Moore wrote
It's usually 1/4WL long. The theory is to turn that 1/4WL of
feedline into a transmission line where the currents on the
outside of the original shield are balanced by the inside
shield on the sleeve which balances the antenna currents.
It functions over a certain single bandwidth.