Reg, G4FGQ wrote:
"Its so simple it doesn`t occur to Terman and other "beings" to mention
it."

Well, Ed Laport had experience with many high-powered transmitters, so
it occurred to him to mention antenna Q in "Radio Antenna Engineering".

Ed assumes power in a dipole is all radiated and none is used to heat
the dipole. Radiation resistance of his horizontal dipole is a function
of its height above ground.

To calculate the Q of the antenna, he first calculates a factor "m"
which is the ratio of the attenuated voltage 180-degrees from the
generator on an infinite line to the generated voltage:
m = Zo-radiation resistance / Z0+radiation resistance

Then: Q = 1+m / 1-m

Radiation resistance = 276 log l/rho

where l is the total length of the dipole, and rho is the radius of the
conductor in the same units.

Laport is interested in antenna Q to make sure the antenna won`t plume
at maximum voltage.
Ed picks a wire size and computes maximum voltage at the antenna tips to
make sure that under assumed conditions the voltage is below the corona
firing potential. The calculation is on page 241 of "Radio Antenna
Engineering".
A trial wire size has a radius of 0.102 inch.

m ccomputes as 0.84

Q computes as 11.4

Balanced dipole feedpoint volts are picked as 690 rms from the
unmodulated applied power.
Volts at the ends of the dipole a
QV/2=3950 volts as rounded.

Corona is initiated on peaks and a further safety factor is added to
avoid pluming, but that`s the way a wire size might be checked.

Best regards, Richard Harrison, KB5WZI