As a competent and experienced engineer, it should then be simple for
you to answer the following:

What is the gain difference, in dB, between a dipole resonant at 97.5
MHz (the geometric center of the FM band) which is 1 mm diameter and one
which is 1 cm diameter? Feel free to assume that the conductor is
perfect, or use copper if you prefer.

Also feel free to calculate the antenna Q and "antenna potential",
although the question here is about gain.

Roy Lewallen, W7EL

Richard Harrison wrote:
Roy, W7EL wrote:
"That`s interesting.(I don`t know why you want fat. It will give you
lower gain.) How much lower? Why?"

It`s a fact. Fat antennas have more bandwidth, and that is inversely
proportional to Q. Teducing antenna Q, by fattening the antenna, reduces
the antenna potential by about the same factor.

Best regards, Richard Harrison, KB5WZI