Topband: Asymmetric radials for GP antennas; Just in case others seek what I've just found...

k8gg at voyager.net k8gg at voyager.net
Mon May 16 20:16:50 PDT 2011



Cormac & other Topbanders,

In the new June 2011 issue of
QST, page 42 there is an article about a vertical with only two
radials on one side of a vertical radiator, and the directivity one
gets by having losses in other directions with a very limited radial
field or ground plane.

If you can model your situation, you can
get a pattern that will tell you about your compromise of having good
radials only over 180 degrees.  One of the W1-land DXers
said he did very well with a good set of radials over 180 degrees and very
little on the other 180 degrees due to site constraints.

One of
the W8's has a vertical near his house and has put radials across the
ceiling of his cellar to fill in the ground plane.  I did that at my
first QTH as well, with elevated radials across the ceiling joists of a
one-story house that seemed to work OK for me with random
length elevated radials anywhere from 50 to 100 feet long behind the
house to the trees and fencing at the perimeter of the lot.

I
have heard of others running radials through "crawl space" where
there a house was built with no cellar and raised maybe 3 feet above
ground level.

Good luck,

73,  George 
K8GG


> All, 
> 
> I've been searching
for clarity and hard data on the effects of asymmetric 
> radials
on radiation patterns and efficiency of a vertical as I'm 
>
installing 
> a 21m vertical for 80/160 and will have to live with
a radial system that 
> is 
> significantly compromised
over a 180 degree sector. 
> 
> I was a bit surprised to
"not find" this subject dealt with in any clear 
>
decisive way in e.g. the ARRL Antenna Book or ON4UN's otherwise excellent

> Low Band DXing book (Did I miss it in either publication? If
so, just send 
> me a "your an idiot" email and I'll
crawl back under my cabbage leaf 
> suitably chastened). 
> 
> I was surprised as I had always assumed it is something
many hams have to 
> deal with unless they are prepared to go on
"stealth missions" in the dead 
> of night to lay
radials on or under neighbours property (I don't recommend 
> this
course of action by the way; I attempted just such a thing once and 
> got 
> caught. As a mental exercise to occupy you during
those quite times when 
> calling CQ on a dead 160m, try
explaining your way out of that one). 
> 
> On the basis
that there might be one/some/many out there, who, like 
> myself,

> are installing verticals with radial systems that are
compromised 
> directionally as well as "length-ways", I
just thought I'd share what I 
> found; N6LF's excellent (if not
exactly encouraging) summary of the 
> consequences of
asymmetrical radials at 
>
http://rudys.typepad.com/files/qex-ground-systems-part-7.pdf . It's well

> worth the read. 
> 
> I hope to hear you all on
the far side of the Summer... 
> 
> -- 
> Regards

> Cormac (EI4HQ) 
> [Cork/UTC+1] NNNN++++ 
>
http://86.43.106.118/ei4hq/ 
> http://www.corkharbourweather.ie

> _______________________________________________ 
> UR
RST IS ... ... ..9 QSB QSB - hw? BK 
> 



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