Topband: FEEDING AN END-FED LONGWIRE

[Tom Rauch]

> Well, the radiation may or may not be as described,
> but one thing is for sure:  common mode feeder current
> is exactly equal to the current feeding the "antenna".
> That's physics.

That's an excellent way to put the problem in perspective. That's why
J-poles have considerable feedline radiation, and why "no-radial" verticals
and end fed Zepps have such horrid problems with RF in the shack.

However with an exact half-wave antenna and an exact 1/4 wl feeder, the
problem is minimized because the antenna can have a few thousand ohms
impedance (low current) and the opposing feeder wire at least has
differential current in somewhat the right distribution to reduce the RF
problem in the shack, IF the tuner has a real floating output (a Johnson
Matchbox won't be good for example because of the grounded capacitors). The
tuner has to look virtually like a perfect open circuit to ground even with
optimum lengths or the Zepp idea "falls apart".

73 Tom