[TowerTalk] Inv L Directivity

[john at kk9a.com]

Oops,  I should have proof read this!    I meant to say that  this is some 
gain (very little) in the "opposite" direction of the loading wire.





To: TOWERTALK at contesting.com
Subject: Re: [TowerTalk] Inv L Directivity
From: David Gilbert <xdavid at cis-broadband.com>
Date: Fri, 31 Aug 2007 15:40:19 -0700
List-post: <mailto:towertalk at contesting.com>

Could you guys maybe have it reversed?  Every time I've modeled an
Inverted-L with EZNEC the directivity is in favor of the direction AWAY
from the top loading wire.  The only exception I've found seems to be if
I assume perfect ground, in which case there doesn't seem to be any
significant directivity.

To be sure, the "directivity" doesn't represent much forward gain in any
case, and in fact compared to a full quarter wave vertical it seems that
the pattern is simply reduced in the direction of the wire ... not
actually enhanced in the direction away from it.  But the "front/back"
looks like maybe a couple of db which might be worth knowing in some
situations.

73,
Dave   AB7E





john at kk9a.com wrote:
> There is enhanced radiation in the direction of the top loading wire,
> however it is not worth worrying about.  It is about 1db with a 1/4 wl
> inverted "L" that is 1/8 wl. high.
>
> John KK9A
>
>
>
>
> To: towertalk at contesting.com
> Subject: [TowerTalk] Inv L Directivity
> From: Craig Clark <jcclark at wildblue.net>
> Date: Fri, 31 Aug 2007 13:33:58 -0400
> List-post: <mailto:towertalk at contesting.com>
>
>
>>    8. Re: Topband: INV L Directionality
>>
>>
>
> G3XAP wrote a number of articles in RadCom (RSGB magazine) about this
> question.
>
> December 1973 p 842 "160m dx from suburban sites"
>
>
> November 1977 p 858 "The G3XAP directional antenna from the
> lower                               frequencies"
>
> Ashton's conclusion was there is enhanced radiation in the direction
> of the top loading wire. His antenna used a 40-60' vertical element
> and a 130' top loading wire. To get omni-directional performance, he
> added more top loading wires.
>
>
>
>
>
> 73, Craig Clark, K1QX