[TowerTalk] lp V stepIR

[Gene Smar]

Gents:

     Fig. 5 in the URL is a good depiction of how only a few of the total 
elements are actually active on any one frequency.  If one could run similar 
models for increasing frequencies across the design BW of the LP one would 
see the peak current move from the back of the LP (longer elements) towards 
the front.  It is for this reason that the gain of an LP is considerably 
lower for a given boom length than a similar Yagi - only a few elements out 
of the six or eight or ten are active at a time.  However, the SWR is 
maintained at a low level throughout the entire BW, the main advantage of 
LPs over Yagis.

73 de
Gene Smar  AD3F


----- Original Message ----- 
From: "jimlux" <jimlux at earthlink.net>
To: "Tower and HF antenna construction topics." <towertalk at contesting.com>
Sent: Sunday, January 24, 2010 1:30 PM
Subject: Re: [TowerTalk] lp V stepIR


> Stuart Browne wrote:
>> Has anyone built an inverted LPDA?  Not practical unless you have the 
>> land
>> and towers to support it but looks cheap to build and rugged. If you had 
>> the
>> height it looks practical for 7-30 mhz.
>>
>> http://plasma.newcastle.edu.au/plasma/research/tiger/venice/Inv_V_antenna_paper.pdf
>>
>> Stu,
>> WH6H
>>
>
> This kind of thing is a mainstay of the commercial HF broadcasting
> world.. take a look at the TCI website.  They even make ones that
> rotate! (you move the base around)
>
> A HF broadcast station near me (KVOH) has something that looks much like
> this, using two towers.
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