Richard Clark wrote:

Cecil Moore wrote:
Your 11.4 meter value assumes a VF of zero.

A quarter wave tall, two inch diameter coil is not resonant - at least
not at a fundamental in the 80M band.

Nobody said it was resonant. The electrical length at 4 MHz
can be *estimated* from the self-resonant frequency of 16 MHz.

90 degrees at 16 MHz estimates to be approximately
90(4/16) = ~23 degrees at 4 MHz. Dr. Corum's strongly suggested
minimum electrical length for valid application of the lumped-
circuit analysis is 15 degrees.

Let's do a simple calculation to see how much error would be
had by using the lumped-circuit model in the following:

X---15 degrees of 450 ohm ladder-line---50 ohm load

The lumped-circuit model says the impedance at X is 50 ohms.

The impedance at X is really 53.5+j119

According to Dr. Corum, that's the maximum acceptable error
when using the lumped-circuit model. His standards apppear
to be lower than mine.
--
73, Cecil http://www.qsl.net/w5dxp