That's all very nice. Let's see if it's useful for anything.

A while back, Cecil posted a model of a base loaded vertical antenna. It
has an inductor which is vertically oriented. The bottom of the inductor
is 1 foot from the ground and the inductor is 1 foot long and six inches
in diameter. Inductance is 38.5 uH and it's self resonant at 13.48 MHz.
(Moving it very far from ground changes the resonant frequency to 13.52
MHz.)

What's it's velocity factor, and how did you calculate it?

Roy Lewallen, W7EL


Richard Harrison wrote:
Reg, G4FGQ wrote:
"I`m even more certain you will find an equation for inductance of an
isolated wire of length L: and diameter D somewhere in the bibles."

Equation 14 on page 48 of Terman`s 1943 edition of "Radio Engineers`
Handbook is:

Lo = 0.00508 l (2.303 log 4l/d - 1+mu/4) microhenrys

Lo is the (approximate) low-frequency inductance and the dimensions are
in inches.

Terman also gives the (approximate) low-frequency inductance formula of
a single-layer solenoid on page 55 of the same book.

One can find the resonant frequency of the coil when using a known
capacitance to resonate the coil at a low frequency. Maybe a dip meter
could be used. Capacitive and inductive reactances are equal at
resonance. Self and stray capacitances are included with the known value
of capacitance used to resonate the coil at the low frequency. The
resonant frequency is lower than the known capacitance by itself would
produce.

The resonance formula used with the actual inductance of the coil will
give the capacitance of the resonant circuit

The difference between the calculated capacitance and the known
capacitor value is equal to the stray and self-capacitance total, so it
is good to minimise stray capacitance when seeking the self-capacitance
value of the coil.

An ARRL Single-Layer Coil Winding Calculator is a slide rule which makes
things easy.

Best regards, Richard Harrison, KB5WZI