[Antennas] End-fed half-wave religion

[Jim Glover]

> Lets get one straight. A j-pole does work. In fact, properly made its=20
> performance is very close (a little better one way and a little less in=20
> another) to a =BD-wave dipole. There is a complete path for loop current.
> 
> With that said can you now take a look at the "whole system" and see why it=
> =20
> works?

I can see why it works, but I don't think I see the "whole system" quite
the same way you do.  What I see is a feedline, a matching network, and
then, out at the high-impedance end of that matching network, a connection
on one side to a half-wave end-fed antenna, and on the other side of that
matching network, nothing.

It is very similar to having the classical tuned-circuit matching network.
A feedline is attached across a primary coil which is transformed into a
high impedance in the tuned circuit.  Across that high-impedance end of
the matching network is, at one side, the end of a half-wave antenna, and
at the other side...nothing (or else a counterpoise, depending on whose
version of the "bible" you happen to be reading).

Also similar are feed methods involving open line balanced feeders.  In
the classical version (Zepp) we have a quarter-wave length of open feedline,
which (as most are aware) can serve as a transformer from a high impedance
at one end of the quarter-wave section to a low impedance at the other.
The low impedance is the feed end, and the high impedance is at the antenna
end of things, where again, we connect one side of the feedline to a high
impedance end of a half-wave radiator, and the other side to...nothing.
In the more general case, we simply feed the half-wave in the same
fashion with a length of coax necessary to reach back to the station,
and then use a tuner to match whatever impedance we find there.

If in fact the J-Pole can not be considered to be a feedline connected
to a matching network at the end of which we connect one side to the end
of a half-wave and the other side to nothing, then, two things:

1.  There are a lot of mistaken antenna books out there.

2.  The J-Pole isn't an example of the type of antenna I'm talking
about, after all.

I'm talking about end-fed half-wave antennas that have a matching system
of some sort doing a transformation from low to high impedance, with the
high impedance end of that matching system connected on one side to the
end of the half-wave, and on the other side, to... either nothing, or else
a counterpoise of some sort.  I know that many people argue passionately
that the counterpoise must be present, or else such an antenna cannot
logically work.  For the most part, their arguments seem to be a
variation of the explanation of how something like a center-fed dipole
works, with current flowing into one side so it can flow out the other
side.  Others argue that end-fed half-waves (and other types of antennas,
too) are fed not with curent, but with voltage, and that the whole thing
can work just fine with the "other" side of the high impedance, high
voltage end of whatever matching system is used just floating out there,
without any need to pass any current (at least, not beyond what its stray
capacitance can apparently handle).

Isn't it true that a number of these sorts of antennas work just fine
without the counterpoise?  

73,
Jim  WB5UDE