Dear all,

For coaxial cable, at HF, where skin depth is less than the physical
outer conductor thickness, there are 3 conductors.

Conductor (1) = Outer surface of inner conductor.

Conductor (2) = Inside surface of outer conductor.

Conductor (3) = Outer surface of outer conductor.

The return path for (3) is the remainder of the universe. It behaves
as a single conductor transmission line which has calculable Zo and
attenuation. (To keep Lord Kelvin happy). When current flows on it, it
also has a radiation resistance.

The currents in (1) and (2) are always equal and opposite in direction
to each other. They are mutually coupled to each other by line
inductance and capacitance.

The current on (3) is always independent of what flows in (1) and (2)
because no mutual coupling exists between them. However, external
coupling can occur and be deliberately or accidently induced at the
ends of the cable.

Any current which finds its way on to (3), which ought to flow in the
antenna, will result in the coax participating in the radiation
pattern of the whole antenna structure.

BUT IT IS A SILLY QUESTION TO ASK HOW MANY WATTS ARE RADIATED FROM THE
FEEDLINE.

OR, CONVERSELY, HOW MANY MICROWATTS ARE PICKED UP BY THE FEEDLINE ON
RECEIVE.

The feedline cannot be treated in isolation as if it behaves
independently of the antenna. For starters, the radiation resistances
of the feedline and antenna do not add arithmetically. They interact
with each other.

In summary, in your own language, the watts radiated from the coaxial
feedline to a resonant 1/2-wave dipole, without a choke balun, can be
forgotten about. There may even be a small advantage. Nothing is
wasted where there are pigs.
----
Reg, G4FGQ