[TowerTalk] Telrex TB4EC stories

[RICHARD BOYD]

Interesting.  Some of the new crop of commercial yagis have a lot of sag 
too, because they use a rapid taper element design that ends in very small 
diameter stuff, and they "whip" a lot in the winds, but apparently survive 
pretty well.

On the other hand, some of the current mechanically "modeled" (as well as 
electrical) homebrew Yagis, like for 40M, have less sag than in previous 
designs because of heavy tubing, more double-telescoped tubing, etc.

I always thought the old 40M Yagis with LOTS of element sag, like in the 
"Gil" cartoon, were "classic," had a classic look.  Then again, it's cool in 
a different way to have a fullsize 40 with little sag.

73 - Rich, KE3Q


----- Original Message ----- 
From: "F. Davis" <fdavis at nfld.net>
To: <towertalk at contesting.com>
Sent: Wednesday, March 02, 2005 4:16 PM
Subject: [TowerTalk] Telrex TB4EC stories


> I have been reading with interest the exchanges about Telrex antennas. 
> Back in about 1991 I bought a brand new TB4EC from the Telrex factory for 
> $375 + $90 shipping to Newfoundland.   I was told it was the last one on 
> the shelf.  I ordered it because I had been looking at Telrex ads for 
> years and was wooed by the supposed quality and ruggedness.........and I 
> needed a small yagi due to space considerations.  I had been using a 
> monoband homebrew 20M  2 el yagi and this TB4EC was not much bigger and 
> would give me two more bands.
>
> The first winter ( I think 1993) that I had this yagi in the air at about 
> 45ft....the reflector element for 20M ( which is linear loaded with a 
> hairpin) actually tore the end off the boom!.  As you know the Telerex 
> elements pass through the boom.  There is a 2.5inch sleeve for added 
> support  but the holes for the insulators for the reflector element are so 
> big that there is not enough material left in the end of the two inch boom 
> to withstand the continuous movement of the reflector.  I called the 
> Telrex people to try and get another boom but of course by then there was 
> no answer to my calls and I guess they were out of business....  I had to 
> have a local machine shop make a 12 inch long end piece to fit over the 
> end of the boom and with the necessary holes to accommodate the 
> insulators.  That end peice was double bolted through the end stubb of the 
> boom and is still there today.  The next winter the antenna was subjected 
> to several ice storms and one storm in particular was
>  very bad .  The icing was built up to about one inch radially on the 
> elements...some how they did not break but when the ice fell off the 
> elements , particularly the driven element and the 20M reflector did not 
> return to their orgionally shape .  They were severely buckled and 
> unsightly.  I took the antenna down in disgust and stored it for 10 years 
> in my barn.  For some reason I couldn't bring myself to throw it out.
>
>  In the summer of 2003 I resurrected the Telrex and took it completely 
> apart.  I replaced the sheet metal screws and straightened the elements . 
> I then ran short sleeves of tubing over the spots where the elements were 
> straightened out to give some added strength.   I put a new balun on it 
> and erected it on the tower here at my new QTH....I added another U Bolt 
> to give strength to the boom to mast joint since the orgional Telrex 
> design called for ONE U bolt through the boom to hold the antenna to the 
> tower.  Last winter 2003/2004 I actually was happy with it as it has some 
> front to back , about 12-15db which is a ll you can expect from 2 ele and 
> a very noticeable pattern.    This winter we have had a lot of icing and 
> high winds.  The winds here will gust to 100kmph on a routine basis so an 
> antenna with ice on it is in real trouble.   The last storm was during 
> NAQP RTTY weekend.  There has been some damage to the elements in that the 
> driven ele and the 20M reflector have take
>  n on a definitive bend in a horizontal direction.  also there is 
> intermittent high SWR on 15 and 20M probably caused by some problem with 
> a screw at a 10M trap.   Also I have always wondered about the tubing 
> joints near the traps .  There is not a tight fit there and always some 
> play in the junctions.  The tubing sizes just don't match well .
>
> Anyway I just wanted to add my experiences with Telrex here in 
> Newfoundland.  Its just a very small antenna , only an 8ft boom and it 
> weighs only 30lb so you'd think that it would last.  Generally the 
> mechanical design is very poor in my view.  For instance the tips of the 
> 20M reflector are 3/4 inch tubing !!.....very heavy and you can see the 
> sag in the elements.
>
> 73 Frank VO1HP
>
>
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>
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