Jim,
While I agree with most of you're writing I think you'll be hard pressed to
get a solid 9 square inches of surface contact in your 1 inch tube with 3
inches of overlap. Maybe if you put in a lot of SS screws or rivets at the
joint. If you're using any kind of joint compound, like Penetrox, you need a
certain pressure to make a good contact, as I'm sure you know. SS hose clamp
+ SS screws has been a good combination for me.
Bert VE3NR
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Thomson
Sent: Tuesday, March 08, 2016 10:46 PM
To: towertalk@contesting.com
Subject: [TowerTalk] F12 C19XR Rivets
Date: Tue, 8 Mar 2016 15:22:32 -0500
From: "Bert Almemo" <balmemo@sympatico.ca>
To: "'Roger \(K8RI\) on TT'" <K8RI-on-TowerTalk@tm.net>,
<towertalk@contesting.com>
Subject: Re: [TowerTalk] F12 C19XR Rivets
I learned long time ago that using pop rivets, blind or not, don't make for
a good electrical connection. For all antennas, using aluminum tubing, I've
used self tapping screws for the last 30 yrs and it's served me well. It's
also much easier to take antennas apart and put them together again using
screws. As always, OMHO!
73 Bert, VE3NR
## The electrical connection is between the mating aluminum tube surfaces,
not the rivets/
self tapping screws. A 1 inch OD al tube, with say a 3 inch overlap, will
have 9 square
inches of surface contact. Unless the self tapping screw is SS, it will
rust. If it is SS, then
you have the dissimilar metal issue. Mosely etc, uses SS self tapping
screws, and they work
just fine. Heck, I used a single slot + SS hose clamps for several years
on my hb yagis...and
they worked just fine, with 100% of the RF flowing through the mating
surfaces. Hy-gain, wilson
etc, used those compression clamp assys....which I just hate with a passion.
Local fellow here had a
hy-gain 204BA up 100 ft near a cliff edge, and after a few years, some of
the tips and inner sections
were just about ready to pop right out. They had migrated outboard quite a
bit. Same fellow also
had the old KLM 4 el 40m yagi......and it self destructed. It was new at
the time. He ended up
buying a bag of SS self tapping machine screws, and drove em in everywhere.
Problem solved
with the ele migration problem. Next problem was the KLM 40 eles came right
off the boom.
The 'fix' for that was to use multiple SS hose clamps to hold the lexan
brackets to the boom.
Then drive SS self tapping screws through the slots on the SS hose clamps.
## I have never seen SS self tapping machine screws ever loosen up, they
seem to hold stuff
together quite well, just don't crank em in too tight, into al tubing,
such that they strip out.
Jim VE7RF
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