Topband: Tuning elevated radials

[Mike Harris]

G'day all,

----- Original Message ----- 
From: "Phil & Ann Duff" <na4m at arrl.net>
To: <topband at contesting.com>
Sent: Friday, September 16, 2005 4:11 PM
Subject: Re: Topband: Tuning elevated radials


| The KJ6GR article referenced "HF Antennas for all Locations" by Les
| Moxon G6XN where Moxon discusses radial current imbalance and
| recommends radials less than .25 wl.
|
| Among the summary conclusions reached by K5IU
| .25 wl is worst possible radial length for current imbalance in
| elevated radials.
| .125 wl radials fed thru a common radial inductor have much less
| current imbalance vs .25 wl radials with no significant reduction in 
bandwidth.

I was going to refer to the G6XN recommendation.

I have used this technique on my 30M vertical.  The vertical element is 30 
feet long with the base 3 feet from the ground.  Two gull wing radials 
then rise at 45 degrees to a height of 6 feet, then horizontal to the end 
supports.  The radials are less than the length required to naturally 
resonate the vertical and connected to a common loading coil then the to 
coax as normal and a large coax choke.  The off centre feed caused by the 
oversize vertical element gives me a pretty good match to 50 ohms, exactly 
as predicted by modelling.  I don't have any other 30M antenna to compare 
it with, however, it does a good job with the DX.

Apologies for the high frequency reference.

Regards,

Mike VP8NO