Hi Chris,
> I am in the process of restoring a Telrex 40M329 beam. I would like to
> contact anyone with experience with this beam and especially someone who
> is still using this fine antenna.
I have a 40M346 or whatever the long boom 40 meter antenna is.
You really need to check some things on that antenna, if it is
anything like mine.
Telrex used two types of elements. The piece going to the boom is
OK, but the next taper has a single wall really thin tubing element
(as I recall something like .038 wall). Some beams use two thin
walls sleeved.
I strutted the elements on mine with tarred nylon supports, but that
wasn't enough. After a few $400 trips by a crane to repair
elements, I just totally rebuilt the elements using normal 6061T-6
.058 wall aluminum with a normal element taper.
Now the antenna has finally lasted six months without a repair.
I also found the stock balun was junk. It had a small coil of coax
and a hunk of house wire in the balun. This balun is probably
different than yours, since my antenna has a 50 ohm feed it uses a
1:1 balun. I replaced it with a homebrew balun. You probably don't
have the same balun, but the obvious design flaws in my antenna's
factory balun make me wonder how good the other baluns are. I
have no idea if the other baluns are OK, just that the factory 1:1
balun that came with my antenna was poor.
The director tuning was OK, but the reflector on mine (using factory
elements) was far too low in the band. When I shortened the
reflector, F/B ratio became around 40 dB or more (measured)
compared to a pathetic 15-20 dB stock at the band center. Your
antenna is different, and may be OK.
The antenna worked OK with factory reflector settings, but I found
them more for feedpoint impedance than F/B ratio. When I reset
the reflector (by watching F/B on a test tower 500 feet away) the
feedpoint was way off.
> Also I am interested if anyone has tried using this beam on 20M by
> altering the feed system and using an antenna tuner?
I don't see any easy way to do that, I think you'd be asking for
trouble.
73, Tom W8JI
w8ji@contesting.com
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