[Elecraft] Counterpoise on 1/2 wave long wire

[David A. Belsley]

Ron:
  You give electrons a lot of credit for intelligence.  A multiple cp must 
be separate wires.  When you are transmitting on a given qrg, the cp that 
is close to 1/4 wave will provide an "input" to your ground that is very 
low impedance.  The others will present varying impedances, but the fact 
that there is one with a low impedance is what provides the RF ground.  If 
you tie them together, as far as the RF is concerned, it is just one long 
wire and the RF in each of your "nubbed" sections is now the sum of its 
presence in all sections -- remember, RF rides on the surface of the 
conductor, and so this is just one conductor with a changing surface area, 
not a changing impedance.

  Also, the placement of the cp should not be parallel to the radiator and 
should not be close to it.  The cp is is many ways acting as part of the 
radiator.  Run your cp away from the antenna and keep the hot ends well 
insulated from nearby objects -- including other nearby cps.  You can run 
the cps parallel to each other, but split the individual sections off 
several feet from end.

best wishes,

dave belsley, w1euy
--On Friday, August 15, 2003 1:57 AM -0600 Ron Pyle <raple@gwtc.net> wrote:

> I'm new here and to ham. I didn't post to talk about me. I have a
> question about the counterpoise on a 1/2 wave long wire. I've been
> reading posts about them.
>
>     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.
>
> RonP
>
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----------------------------------
David A. Belsley
Professor of Economics