Bill- Most probably it's because the connection is not really "sealed".
There are usually microscopic crevices betweeen parts where moisture vapor
can enter, and this vapor may condense into water - eventually contributing
to galvanic corosion. Albeit, some of the "peaks" in material should still
contact, but in general, the connection is prone to degradation over time.
I always tin (with solder) any copper plated wires that contact my
galvanized tower. Solder is a good intermediate metal that is easy to apply
to copper while being much more compatible with galvanized (zinc) surfaces.
I've never connected stainless steel guys to my tower. In any case, if you
(1) assure that the surfaces are clean, (2)seal out moisture by using
conductive grease, and (3)further protect the joint by using a
self-vulcanizing tape, etc. then you should have a reliable bond that will
last until you decide to take it apart. I might mention that you need to be
careful in your choice of the outer protection - whether it be
self-vulcanizing tape, "liquid tape", or whatever because of long-term
exposure to ultra-violet radiation (from the sun). Unfortunately, very
little attention is focused in amateur radio publications about material
compatibility and long-term reliability of materials and electrical bonds.
Hopefully, someday, the ARRL Antenna Handbook will include a chapter on
this subject, and all articles on antennas will be screened to ensure that
they are in agreement with acceptable practices.
May I add, that many years ago when I lived in Southern Nevada, we mixed
aluminum and copper hardware with no problems whatsoever. That was due to
the very dry climate that was the rule in those years. With the growth in
population (more lawns, swimming pools, etc.), I'm quite sure that that
wouldn't be the situation today. When I was in 4X, I soon found that my
Southern Nevada bonding practices wouldn't work over time. The point here is
that some amateurs who see the above comments will say "nonsense, I never
bother with those things, and have no problems". That is probably true for
those who are blessed with an extremely dry climate :-)
73,
Riki, K7NJ - 4X4NJ
-----Original Message-----
From: Magoo [mailto:magoo@isp.ca]
Sent: Sunday, September 05, 2004 4:44 PM
To: R. Kline
Subject: Re: Topband: TOP HAT GUY WIRES
Riki-did you take the guy wire directly to the electrical connection on the
tower or use another connecting wire like braid? I do have Noalox and I
also have a material to seal the connection from the weather. I just can't
figure out why the connection would go bad when it is mechanically tight on
clean material and "sealed" from the weather. But the Noalox sounds like a
good thing to try after I clean up the connections.
Thanks for your input.
73,
Bill
----- Original Message -----
From: "R. Kline" <k7nj@zahav.net.il>
To: <topband@contesting.com>
Sent: Sunday, September 05, 2004 3:21 PM
Subject: RE: Topband: TOP HAT GUY WIRES
> I've had good results with similar connections by using a suitable
> conductive grease. I believe that these are mentioned in the ARRL Antenna
> Handbook. I've used both "Noalox", and "Penetrox". Be sure to use the
> right kind of Penetrox as the manufacturer makes several. AES sells the
> correct kind of Penetrox in a small squeeze tube. Noalox is commonly
> available wherever electrical supplies are sold for professional
> electricians since it is commonly used to assure long-term reliable
> conductivity of conduit connections, etc.
> 73,
> Riki, K7NJ - 4X4NJ
>
>
> -----Original Message-----
> From: topband-bounces@contesting.com
> [mailto:topband-bounces@contesting.com]On Behalf Of Magoo
> Sent: Sunday, September 05, 2004 6:53 AM
> To: topband@contesting.com
> Subject: Topband: TOP HAT GUY WIRES
>
>
> For those using "aircraft" control cable or similar stranded galvanized or
> stainless steel wire as combined guy wires/top hat loading wires, did you
> take any special precautions in attaching to the mast/tower for good
> electrical conductivity?
>
> I installed lengths of tinned braid under the guy wire clamps, and
attached
> these to the tower with burndy connectors, but have discovered some
evidence
> that the braid/guy wire connections have begun to break down after just a
> couple of years. I'm not sure if it is arcing (seems impossible with the
> mechanical nature of the connection) or galvanic, but the connections are
> not like they were when installed even though protected from the elements.
>
> I cannot use copper wire for these tophat/guy wires as the load would be
too
> great in the wind/ice conditions we sometimes encounter at this QTH.
> "Aircraft cable" was the only choice possible.
>
> Any ideas or opinions about this situation would be appreciated.
>
> Bill, VE3NH
>
>
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