[TowerTalk] Coaxial Inverted L

[Thomas Giella KN4LF]

This is the antenna that Bruce WA3AFS uses. http://www.kn4lf.com/kn4lf3.htm 

--... ...--,
Thomas F. Giella, KN4LF
Lakeland, FL, USA
Grid Square EL97AW
kn4lf at arrl.net

KN4LF Amateur & SWL Radio History: http://www.kn4lf.com
Radiowave Propagation Yahoo eGroup: http://groups.yahoo.com/group/radiowavepropagation 
  ----- Original Message ----- 
  From: K4SAV 
  To: towertalk at contesting.com 
  Sent: Thursday, July 13, 2006 7:09 PM
  Subject: Re: [TowerTalk] Question on Multiple Inverted L Antennas


  ..."Here we go again... so which is it? Inverted L's have plenty of 
  bandwidth or Inverted L's little bandwidth??? "...

  The traditional L with a good ground doesn't have much bandwidth. But 
  WA3AFS doesn't have a traditional L. Unfortunately, from his description 
  I could not decipher exactly what his antenna looks like. It is possible 
  when using coax as an antenna element, and playing games with shorts at 
  the right places, to produce something with double resonances, which may 
  be what he has. NEC based tools can't analyze antennas such as this, so 
  experimental data may be all the data you can get.

  A better description of this antenna might be useful to some of us.

  Jerry, K4SAV

  Robert Chudek - K0RC wrote:

  >Gentlemen...
  >
  >Here we go again... so which is it? Inverted L's have plenty of bandwidth or Inverted L's little bandwidth???
  >
  >First, let me say if you are not taking your measurements AT THE FEEDPOINT, you are not seeing the true story. Second, a large bandwidth is not necessarily a good thing. The longer and more lossy your transmission line, the better your antenna is going to look from the shack.
  >
  >Here's an example of what I'm talking about... I have a low 160m inverted vee which I plotted VSWR graphs at the feedpoint and again at the end of 230 feet of rg8x coax. I made absolutely no antenna changes between these two measurements. I posted the superimposed VSWR and RETURN LOSS curves on my website, here: http://tinyurl.com/oh87y  The two PDF files are 72-KB each and can be downloaded and viewed using Adobe Acrobat Reader.
  >
  >In this specific example, measuring at the end of the coax leads you to believe you have 35% better bandwidth than in reality.
  >
  >73 de Bob - K0RC
  >
  >
  >
  >  
  >
  >>On 13 Jul 2006 13:20 WA3AFS wrote:
  >>
  >>Please be aware that the bandwidth for a coaxial inverted L is very 
  >>broad.  My SWR at 1.800 is 1.3 and slowly rises to 1.7 at 2.000Mhz.
  >>
  >>    
  >>
  >
  >But then on 13 Jul 2006 at 13:11, K4SAV wrote:
  >
  >  
  >
  >>>The biggest problem you have with low band multiple L antennas is 
  >>>matching and bandwidth. To start with, a 160 meter L will not have a lot 
  >>>of bandwidth...
  >>>      
  >>>
  >
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