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[TowerTalk] TelRex Rotor

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Subject: [TowerTalk] TelRex Rotor
From: (Rich L. Boyd)
Date: Wed, 2 Apr 1997 01:04:23 -0500 (EST)
N4SI asks about Telrex antennas.  I didn't come into ham radio until 
relatively recently ('65, hi) so I don't know much about it prior to 
that,'s my understanding and observation.

Telrex, in its day, made the biggest, heaviest, and most effective, world 
class yagis, kind of the antenna equivalent of the 75A-4/KWS-1, or Rolls 
Royce or something.  Expensive too.  The company was built up by Mike 
Ercolino.  When his son, Charles took over things seemed to go downhill.  
When I spoke to Charles on the telephone he always seemed to resent 
inquiries about the product line; I'm not talking about complaints.  They 
seemed to have a practice of insisting on the serial number of the beam 
you were calling about before they'd answer questions -- it did seem they 
only wanted to deal with original buyers.  My impression was they were 
paranoid about people stealing their designs.  The company eventually ceased 
production.  A few years ago I did succeed in getting a telephone number 
for them from the information operator and they were accepting telephone 
calls on Tuesday and Thursday mornings to sell parts.  The prices seemed 
high to me, like $120 for a 12' piece of 1" aluminum tubing swaged at one 
end.  I concluded I'd cannibalize other antennas (and/or homebrew parts) 
instead.  I don't expect to go to Telrex for parts again, if they're 
still selling them.

Telrex antennas were designed with the old cut and try method and tested 
on a bona fide test range.  They were very effective antennas.  Now we 
have computer modeling of antennas and designs that are apparently 
superior.  But...the "good ole" Telrex antennas still seem to work.  
Telrex antennas were made so heavy (strong) that they can be "rotator 
busters."  A prop pitch or comparably husky commercial rotator 
(expensive) are good choices for the larger ones.  But...I've been 
turning a 6-el 10 stacked with 2-el 40 on a Tailtwister for a couple 
years and haven't busted the rotator yet.  The 8-el 15 stacked with a 
6-el 20 are turned with a prop pitch though.

The Force-12, by comparison, uses a nice rapid taper design that makes 
for a very lightweight antenna, a tremendous advantage in installing, 
maintaining, and rotating.  We've seen messages on the reflector about 
the varying SWR when those lightweight elements whip around.  But, this 
apparently doesn't cause any problems.  The Telrex elements (except on 
the 40 whose elements are more like Force 12 in a way) don't move much in 
high winds.  There's talk of the advantage of an antenna shedding 
elements in extreme wind and at least the tower is saved.  A Telrex 
antenna may be more likely to "shed the tower," which of course will 
wreck the antennas too when the tower falls out from under them.

Telrex used a "through-the-boom" element mounting design which is 
attractive and tends to keep the elements in the same plane, which is 
nice looking.  But...after some years an element or two will develop 
enough play that they start reaming out the "through the boom hole."  
Then you get a floppy element and eventually the boom will split at that 
point.  I have a 5-el Telrex tribander with a boom that's split like this 
-- it's adequately patched together and I use it for field day.  And 
there are ways to homebrew a fix for the reamed-out-hole problem.  
But...the clamp on the elements one at a time on plates using a tilting 
boom to mast mount (PVRC mount) system is much more convenient at 
installation time but even more so when an element repair is needed.

Telrex put a lot of elements on the boom of some of their models, like 10 
el on 10M on a 48' boom, 6 on 20 on 46' boom, 8 on 15 on 45' boom.  
Computer modeling indicates 7 on 10, 5 on 20, and 6 on 15 on these boom 
lengths works just as well (or better), making for a lighter weight 
antenna, hence easier to install and rotate, and an antenna with less 
wind load.  And, the modern computer designs don't equally space the 
elements like Telrex did.

A few years ago W0YVA and I talked about Telrex and said "Somebody should 
see if Telrex will sell their name and their inventory, their machine 
equipment, etc."  I guess we concluded that someone wasn't us, or at 
least not at this time, because neither of us did a thing about it except 
They were very well made antennas. 
The mechanical design could definitely be updated and improved.  And the 
electrical design could be redone with the aid of computer modeling.  
It's a shame Telrex didn't stay in the business and keep improving on 
their fine antennas.

I'm told there has been some computer modeling redesign done on the 
Telrex antennas (not by Telrex but by individuals) -- element lengths at 
least and maybe spacing too.  To 
change spacing you'd have to drill more boom holes or use clamps.  You'd 
basically end up with a homebrew antenna that used Telrex parts, which is 

Summary:  Nicely made, expensive, heavy duty antenna.  Incrementally 
inferior performance-wise, at least theoretically, to modern computer 
modeled designs.  Mechanical improvements (clamp-on outside the boom 
plates and lighter weight) could help.  73 - Rich Boyd, KE3Q

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