[Elecraft] Counterpoise on 1/2 wave long wire

[Don Wilhelm]

Ron,

First, what you are describing (wires parallel to the radiator) is not what
we most commonly call a 'counterpoise'.   A counterpoise normally consists
of a quarter wave wire at the frequency of operation.  The near end will
have a low impedance when the far end is open (CAUTION - the far end will
have a high RF voltage on it).  What we commonly refer to as a counterpoise
is not placed parallel to the radiating element, but is placed at any point
in the antenna system that you want to create an RF ground point without
requiring a connection to an actual earth ground.  It normally is placed
perpendicular to the radiating element(s)- the radials on a vertical
monopole is one example.  Placing them in parallel with the radiator will
cancel part of the radiation.

Secondly, the wires of a counterpoise must be separate if they are to be
seen by the antenna system as quarter wave wires.  RF does not behave the
same way as DC in chosing the path for current.

I believe the antenna you are describing is some multi-band adaptation of
the original Zepp antenna.  The Zepp is a half wavelength endfed wire with a
quarter wavelength wire in parallel at the feedpoint end.  Both wires are
required - consider both of them as part of the antenna.  This antenna has
no 'magic' to it, it was a very useful configuration for its intended
purpose - the antenna 'trailed' from a single support point on an airborne
vehicle (often with a flag attached!!!).  The radiation is similar to that
obtained from a dipole, but the feed was more convenient in that situation.

A balanced feed antenna system (like a regular dipole) is normally better
behaved than asymetrical antenna configurations.  I would recommend them
over end fed wires because they are already balanced and usually are free of
'RF in the shack' problems.  Unbalanced antennas can be difficult to tame -
but they do work, and in some instances, work very well - just be prepared
for a lot of cut and try with them if they exibit 'funny' behavior.

73,
Don W3FPR
----- Original Message -----

    Take a 1/2 wave long wire for multiband use, 80m lowest. The
counterpoise's I've been reading about want several insulated wires at 1/4
wave for each band, tuned. Best placement is about a foot away and running
parallel to the 1/2 wave antenna wire. Now these counterpoises are all
connected to the shield of the coax (ground). Electrically, I can't see that
there is a need for insulation between these wires in the counterpoise?
Isn't the frequency in use seeking the end points? Otherwise the wires of
the counterpoise are electrically together...correct?

    After all. The frequency is being dictated by the hot long wire. Not the
counterpoise. The counterpoise is working as a reaction to the long wire and
ground, and it's placement between the long wire and ground.

    If I am correct. Why can't this counterpoise be made of one wire with
several small nubs (wire) soldered at the 1/4 wave points of each band? Even
go and sharpen the nubs to better increase their electrical appearance as an
end point.