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[TowerTalk] 17M Wonder Bar Antenna

To: "" <>
Subject: [TowerTalk] 17M Wonder Bar Antenna
From: Doug <>
Date: Wed, 20 Dec 2006 11:01:05 -0500
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In reading the Jan 2007 issue of 'QST' I came across the article, "17 Meter 
Wonder Bar Antenna".  This antenna appeals to me due to the fact of low wind 
resistance, the ability to use a TV rotor to turn it, and I have all the 
materials for construction.  However, the article left me with a number of 

1.  No formulae were given to scale the antenna up or down to suit other 
bands.  I have built a number of yagi antennas and I generally understand how 
to formulate changes for given bands.  However, this antenna has shortened 
elements, in a bow-tie configuration, and therefore I do not have a clue how to 
figure the boom spacing of the elements, size of the elements, or the coil size 
required.  I would like to understand how to compute dimensions for shortened 
element antennas.

2.  This particular antenna uses coils wound on 1" ID PVC.  Would an air wound 
coil be more efficient or have an advantage over this design?

3.  The author capacitive couples the feed line to the coil of the driven 
element.  Is there a more efficient or solid means of connection?  Would anyone 
have a guess as to the power handling capability of such a setup?

4.  Tuning the coils to make the elements resonant left me a little fuzzy.  If 
I construct the coil / element assembly how do I properly attach my MFJ-259 
(Pre B Version with only the PL-259 connection) to the coil?  Does a reading of 
the lowest SWR actually indicate resonance?  I also have a grid dip meter if 
this would provide a more useful measurement of resonance.

I fully understand that this antenna is not the most efficient design that I 
could use.  However, for the reasons stated above, it definitely would work 
well in my location.  This will all become a moot point when my 80? tower is 
erected, but until such time, this should provide me with a decent antenna at 
little or no cost.

Thanks for your assistance,

Doug Coffman ? N9XTF


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