[TowerTalk] Hy-gain 204BA element changes...

John Wagner jwagner at dxengineering.com
Mon Feb 20 08:46:42 EST 2006

> I have an older Hy-gain 4-element 20 meter mono band beam.  I 
> downloaded the LJ-204BA manual from the Hy-gain (MFJ) website.  I 
> took the antenna apart and verified that all the element lengths are 
> the same in the manual.  Other than a different style hairpin, my 
> older antenna is identical to the current version.
> Hy-gain makes use of swagged element tips.  I have a slight issue 
> with the amount of overlap with the non-swagged elements 
> closer in to the boom.
> I'm aware of the electrical characteristics of tapered elements and 
> know you just can't shove one the second element in and extra inch 
> and make up for it by pulling out the third element an inch.  The 
> diameter of the tubing effects the electrical length of that 
> half-element.
> Well, understanding, and knowing how to compensate for changes, is 
> two different things and I could use your help.
> I can download a YAG file from the ARRL website 
> (http://www.arrl.org/antmodels/), but need YO to play with it.  I 
> believe YO compensates for tapers.  I don't have a NEC file 
> of this antenna.
> So let me get specific...
> The second tube out from the boom (for all eight half-elements) is 1 
> 1/8" x 48".  The instructions call for 46" exposed.  This leaves only 
> 2" inside the 1 1/4" tube!  The 1 1/4" tube is NOT swagged.  The 
> third tube out is 7/8" x 55".  The instructions calls for 50 1/2" 
> exposed.  This leaves 4 1/2" inside the 1 1/8" swagged tube.  Here is 
> the thing though, the 1 1/8" tube is swagged for the first 2".  The 
> remainder 2 1/2" of the 7/8" tube if just floating inside the 
> 1 1/8" tube!
> What I would like to do is move the 1 1/8" tube in one additional 
> inch (3" overlap instead of 2") and compensate for the shorter 
> half-element by pulling the 7/8" out...but by how much, I don't 
> know.  I have 2 1/2" to play with since it is only floating in 
> air.  This is where I need your help!  I do know that 1" of 1 1/8 
> requires more than 1" of 7/8" to compensate.
> The rest of the elements have enough overlap per diameter.  My issue 
> is that there is a lot of weight on only 2" of the 1 1/8" tube!  It's 
> a good argument to say this is the way it's been done for years, so 
> why mess with it.  My 1 1/8" tubes are bent at the 2" mark and I'd 
> guess it would be better if there was a bit more overlap.
> One of these days I may get a copy of YO and learn to use it, or 
> build a NEC file for use in Eznec, but for now, I'm useless!  :-)
> Dino...k6rix at earthlink.net  

Dino, I'm with the folks who suggested that making these changes to the 'BA
Is probably not necessary. I have an older (25+ year old) 204BA, bought it
Other than changing the hairpin to the new style, cleaned it up and put it
back up
On my 55' tower. It has been through heavy winds, ice, etc. no problem at
all and works
Very well. I might suggest a balun upgrade to a good current balun rather
than the Hygain
Bn series.

73 John W8JJW

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