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[TowerTalk] Re: Ideal 40m Wire Antenna

To: <>
Subject: [TowerTalk] Re: Ideal 40m Wire Antenna
From: (Tim Makins, EI8IC)
Date: Thu, 27 Sep 2001 08:14:07 +0100
Whoops, yes, I wasn't very informative. The mast is planned to be 80' high,
made of 4 steel 2" scaffold poles. It will be guyed at 4 levels, using
polypropylene rope. Each level will have 4 guys. It will be erected using a
gin-pole, of 30' length, pre-attached to the base of the main mast at 90deg.
No funds are available for rotators, so a yagi is out.

Does this help anyone to comment on my question ?

> Original Message From: <>
> Tim,
> The solution to ANY problem begins with a COMPLETE and
> ACCURATE DESCRIPTION of the problem. You neglected to
> tell us anything about this mast or guys. It would be useful
> to know the material, >construction, size (width), etc to
> have a feel for what it can support. Would it hold a 3L Yagi?  2L?
> If not, a pair of inverted vees at right angles is a good solution.
> Pull the ends out as far / high as possible.
> The effective height of a Horizontally Polarized Delta Loop is
> roughly 1/3 of the it's height above the bottom wire which
> comes out to roughly 50 ft with the apex at 80 ft assuming
> an equilateral triangle.  Better to go with the higher inverted vees.
> I worked my first 300 countries on 40M using various
> Rotary Dipoles at 80 ft.  The feed impedance of a 40M dipole
> at ~90 ft goes through a minimum (roughly 5/8 WL) which
> means that the current (and therefore field strength) will be a
> maximum at the associated peak waveangle.  The net result
> is that you need to go much higher before you realize further
> benefit ( with a dipole antenna) .
> Tom  N4KG
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