Dan, WK8L wrote:
"I think you are confusing the Isotron by Bilal with the Isoloop
formerly made by AEA."

I apologize for causing confusion. The Isotron is only a large capacitor
with a trimmer?

A large capacitor has a low reactance and to form a resonant circuit.
must be paired with an equally low reactance of the inductive variety. A
small rod or a small loop, in terms of wavelength, have similarities.

Terman is much more eloquent than I so I`ll quote from page 907 of his
1955 edition:
"The directional pattern is independent of the exact shape of the loop,
provided the loop is small compared with a wavelength.

The directional pattern of a small loop is identical with that of an
elementary doublet. The only difference is that the electric and
magnetic fields are interchanged. For this reason a small loop is often
called a magnetic
doublet.

The radiation resistance of a loop antenna is less the smaller the loop
area. For the radiation resistance to be large enough to give good
antenna efficiency, it is necessary that the loop perimeter be of the
order of a wavelength."

So the name "magloop" may come from "magnetic doublet". When is a loop
small enough to be a 'magloop"? One requirement may be the same current
in all sides of the loop and I`ve seen that specified as a perimeter of
0.1 wavelength or less. Like many specifications it may be arbitrary.

I suppose calling a capacitor an "Isotron" is arbitrary too.

Best regards, Richard Harrison, KB5WZI