Hello Stan
My note is a little off topic because I like to remove the counterpoise all
together by addressing the issue of common mode current.
I thought that, rather than getting embroiled with definitions, I would
offer something different. You don't say what bands you operate but your
crucial point is you are up in the sky so to speak and I've been there and
suffered accordingly.
*Until recently* no commercial antenna manufacturer had conquered the mighty
common mode current problem of the off-centre-fed dipole. Since you run QRP
you don't need anything big or heavy duty, you might consider the offerings
from Spiderbeam. They currently do a 40m version which covers all bands to
6m and your KX3 will handle any slight mis-match with ease. A friend of
mine ran one of these as a sloper out of his window using a KX3 and got
excellent results. No external tuning box or counterpoise is necessary,
it's all handled in the special dual choke balun. I understand they are
working on an 80m version. I have no commercial connection with the company.
If you prefer to build your own aerials, then you can see the website for
DJ0IP who in my opinion is now the world authority on these aerials having
done more research and *practical testing* than anyone. I doubt if that's
an exaggeration. On his website you will see how to make your own quite
inexpensively. There is also a lively and progressive forum dedicated to
the ocfd.
If you would like to know more, do get in touch.
73
David
G3UNA
ps I use a special version of the ocfd called the end-connected off centre
fed dipole.
----- Original Message -----
From: "Stan GW3SRM" <[email protected]>
To: <[email protected]>
Sent: Saturday, June 10, 2017 7:40 PM
Subject: [Elecraft] Counterpoises and Grounding
I note that the subject of counterpoises has been debated many times in
this
forum but I have not seen the subject of tuneable artificial grounds
discussed. As no doubt many are aware, operating from a location remote
from
the ground has its problems in ensuring effective grounding, especially
with
end fed wire antennas. I have this problem as I operate from an upstairs
shack. I have overcome the difficulty by using a tuneable counterpoise
arrangement in conjunction with my end fed wire antenna. The EFW antenna
is
approximately 66ft (20m) long and the counterpoise wire 16ft (5m).
Using my homebrew AGT and my KX3 is a simple process to tune for
resonance.
a) Tune to the desired frequency using the internal KX3 auto tuner. b)
Tune
for maximum current using the AGT meter (low power recommended for
tuning).
Repeat the process as necessary to obtain best match. Usually 1:0 or 1:1
(KX3 reading). I only operate with 5 or 10 Watts. Apart from overcoming
grounding problems you get a resonate grounding system not an
approximately
resonate one as used in most circumstances. This in my view, is a suitable
compromise in overcoming difficult grounding conditions, although I do not
advocate it in preference to an extensive grounding system where
conditions
permit. One point to note is that if an external power supply is used the
output must be isolated from ground and suitable precautions taken against
lighting strikes. Many designs for simple homebrew AFT projects are
available on the web and MFJ also do one commercially. Obviously different
or different multiple lengths of counterpoise wires can be used to get the
best setup with your antenna.
73 Stan GW3SRM
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