[TowerTalk] Yagis and Rivets
Wed, 15 Mar 2000 23:05:43 CST
Hi Dave; I don't know what manufacturer made ur "C3-S" but I can say
from my personal experience with HyGain, and also to a lesser extent,
CushCraft, I would'nt purchase ANY antenna that was put together w/
rivets. I put up one of the newer Moseley antennas awhile back for a
ham that is now deceased. Just by looking at the construction method
of his antenna (w/ rivets) I knew that I didn't ever want an antenna
that was put together using rivets.
I currently have 4 towers erected on my 2-1/2 acre lot: 2- Rohn 25
(62' & 63') and 2- Rohn 45 (90' & 136'). I am currently using a Hy-
Gain TH7 @ 91'; a CushCraft 40-2CD @ 137'; a CushCraft A3-WS @ 63'
and a home-built COPY of a KLM 30M-3 @ 64'. I am half-way finished
with building a COPY of a Telrex 40M346, which is a 3-el. (full size
elements) 40 meter yagi on a 46' boom. That will replace the Cush- Craft
40-2CD that is my "temporary" 40 meter yagi. Also going up will be HyGain
105BA & 155BA 5-el. yagis for 10 & 15 meters; 2- HyGain 204BAs (one for 20
meters & the other w/ shortened elements, for 17 meters) and a Cush Craft
12-4CD, which is a 4-el. 12 meter yagi. In addition to all of this, I'll be
putting up a M2 80 meter rotatable dipole above the 40 meter yagi on my 136'
The reason why I'm telling you what I've got planned for installing
is that NONE of these designs use rivets. They either use stainless
steel hose clamps, formed stainless steel clamps w/ stainless steel
bolts & nuts, stainless steel bolts & nuts or combinations of the
Before I install ANY YAGI, I always let the antenna sit outside after
it has been assembled & I then re-tighten everything early in the
morning, preferably when the ambient temperature is at its lowest.
That's because the aluminum material has had time to cool down and
contract to a smaller size. Then, when the material heats up & begins
to expand, the fasteners actually become tighter.
I have been an industrial electrician for abt 25 years (I am 48 yrs.
old) and having worked w/ aluminum power-carrying conductors (the
kind that are installed in conduit, connect to disconnect switches
& circuit breakers, etc.) I have learned over the years that it is
MANDATORY w/ aluminum conductors to periodically check & re-tighten
the terminals to which aluminum conductors are fastened. That's be-
cause aluminum, being such a soft material, will in effect "work it-
self loose" over a period of time. In other words, a terminal that
was sufficiently tightened will be found to be somewhat looser, a
year after its initial installation. Many companies have in place a
preventative maintenance program of periodically re-tightening ALL
terminals to which aluminum conductors are connected. This is to
avoid the joint becoming hot, possibly causing the terminal to over-
heat, ruin the device to which it is connected & starting a fire.
That's the primary reason why the practice of wiring houses with
aluminum was discontinued years ago. The associated problems & risks
that were inherent w/ aluminum wiring weren't worth the cost savings
that was to be had by using aluminum over copper wire.
Sorry to have made this so long but the purpose of relating all of
this information to you was to explain why I would have nothing to
do with any antenna that used rivets in its construction.
Best of luck with your antennas. Good DX and 73 de Brad, N9EN
>From: "Dave D'Epagnier" <DDEpagnier@compuserve.com>
>To: towertalk <firstname.lastname@example.org>
>Subject: [TowerTalk] Yagis and Rivets
>Date: Wed, 15 Mar 2000 17:56:04 -0500
>I'm just about to finally put back up my C3-S. It's been up for about a
>year and a half and worked well all that time - no problems. I thought I'd
>maybe redo the joints with some silicone vacuum grease and kind of spruce
>it up a bit before it was put back into commision. One thing noticed on my
>half disassembled antenna though is that ALL OF THE RIVETS ARE LOOSE!
>Sorry, don't mean to shout but this is surprising. It looks to like every
>one of those once very sturdy rivets are loose. I can wiggle every element
>section with respect to its mate and have to wonder how good the rf
>connection is between them. And I thought rivets were the best and would
>never be a problem.They were installed correctly. I'm wondering if aluminum
>rivets are simply wimpy. Maybe steel rivets would hold much stronger and
>longer, and even though they may cause local corrosion, the overall
>connection might last longer with steel. Has anyone else experienced this?
>How did you deal with it?
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