Topband: Low Loops, Tee's and ...

[dick.bingham]

Greetings everyone

I will respond to Jim, who among others, has provided good information about loops and verticals w/without top-hats.
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Date: Mon, 29 Jun 2015 13:49:04 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
To: topband at contesting.com
Subject: Re: Topband: Top hat vertical
Message-ID: <5591AF40.9040000 at audiosystemsgroup.com>
Content-Type: text/plain; charset=windows-1252; format=flowed

> On Mon,6/29/2015 10:30 AM, Tim Shoppa wrote:
> I have had excellent success modeling "Marconi T" verticals with EZNEC. The
> Demo version can do a Marconi T just fine.

Same here. My T vertical for 160 is 100 ft vertical and 82 ft 
horizontal. That makes the antenna resonant below the band, with a 
feedpoint Z of 50 ohms plus some inductive reactance on 160M. I add 
series C to tune out the L. The same idea will certainly work on 80M.

Remember that any vertical needs an effective radial system or 
counterpoise to prevent excessive losses in the earth.

73, Jim K9YC
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Why do not more folks use the Half-Square antenna ? With its Hi-Z feed point it makes a great candidate for areas with poor soil conditions. It's performance here at CN98pi
on 160-meters in a glacial outwash deposited silt/sand/gravel river valley seems to be as good as I could hope or expect. This antenna either works very well OR you guys along the East Coast have superb 'ears' to hear my 100-watts during the contests.

The ground system is a single 8-foot Rod driven into the sandy/rocky soil and the antenna fed through an appropriately "tapped" inductor in a parallel-LC network connected between ground and one of the antenna's end-wires.

In my case, two L/4 end-wires - spaced L/2 - are connected at their top-ends by a L/2 phasing section that is about 90-feet high. As a result, the radiating elements have to slope away (parallel to each other) toward ground instead of a direct vertical drop. 

This antenna appears to play closely to what EZNEC analysis suggests and the necessity of not needing lots of copper in/on the ground to perform well is nice.

73 Dick/w7wkr CN98pi


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