[Elecraft] Counterpoises and Grounding

[David Cutter]

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" <stan.gw3srm at uwclub.net>
To: <elecraft at mailman.qth.net>
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
>