[Elecraft] multiband counterpoise with K1

[George, W5YR]

Andy, I have posted on this topic at least a dozen times over the past
two years.

This "bundle of wires" is not a true counterpoise in any sense of the
word. It is, rather, a "driven ground" in which the wires being in the
near-field of the antenna develop a current and associated voltage. By
being 1/4 wavelength long and open at the "far end" the end attached
to the station equipment is driven by the induced r-f to a near zero
r-f potential, effectively "grounding" the equipment. Generally, this
produces better results that any attempt to physically connect to an
Earth ground. "Ground"is not all that it is supposed to be for r-f
purposes - I suspect that more problems are created by efforts to
"connect the station to a good r-f ground" than by omission of any
such connection and concentration on the antenna system configuration.

Keep in mind that the wires need be only approximately resonant but
length is to some degree important. The open ends can achieve quite
high voltages so they must be insulated. The wires will radiate and
can be a source of RFI. Being bound up in a bundle will detune them
all to some extent, but as long as they "work" that is what counts.

Good luck with your new discovery of a very old application of the
"driven ground."    <:}

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489      Icom IC-765 #2349     Icom IC-756 PRO  #2121


----- Original Message -----
From: "Wallace, Andy" <awallace@mc.com>
To: <elecraft@mailman.qth.net>
Sent: Thursday, December 05, 2002 7:37 AM
Subject: [Elecraft] multiband counterpoise with K1


> > -----Original Message-----
> > From: Thom LaCosta [mailto:baltimoremd@baltimoremd.com]
>
> > FWIW, for years I was frustrated with bad locations, RF all over
the
> > place, etc.....until I made up "The Bundle", a series of 1/4
> > wavelength wires for each band I use.  Taped them all together and
> > stretched it out around the secnd floor of my house.  The antenna
is an
> end
> > fed wire about 89 feet long, and all of 15 feet high.
>
> Thom, thank you for this idea! I just tried it. My ant is just
> a 35' or so random sloping down to a clothesline pole. The rig
> is a fair distance away from the window so I use a length of RG8X
> to get there. I've got a barrier strip attached to the wall and
> the coax attaches here, with the antenna wire attaching to
> the corresponding terminal. So I have the coax shield terminal for a
> counterpoise - in trying a random length of that, it didn't help
much.
>
> I made a bundle as you described for my 4-band K1 (40/30/20/15) and
> drooped it down the stairwell. Seems to work. The KAT1 is happy
about
> it. I'm in MA -- had a ragchew with a guy in NM on 20, and worked
LX0LT in
> Luxembourg on 40 as well. Bands may seem a little quieter -- perhaps
this
> helps on receive also. I'll hang it (unfortunately inside) more
properly
> tonight and keep experimenting. I'll be happy if it reduces TVI,
too.
>
> I don't see any references for such a counterpoise in a quick
search. If
> anyone has pointers, please post them. I am curious how the four
different
> lengths affect each other, electrically. Should the lengths change?
I guess
> it would be similar to a fan multiband dipole, except with the
elements
> against each other. I used insulated wire, of course!!!!
>
> Before someone suggests -- unfortunately I have no prospects of a
better
> antenna outside... :-/  Someday!
>
> -Andy