[TowerTalk] Antenna Grease--Deficiencies and Remedies

[Joe Reisert]

Ken,

When I came to New England from San Jose, one of the locals told me all 
about the silicon grease trick you mentioned so I believed them....for a 
while....However, after a few years, some water apparently did get into the 
connectors one by one and they eventually flashed over. In fact, at 400 
Watts on my 432 MHz EME antenna, the center pin on an expensive 7/8" 
Andrews coax connector had a vaporized center pin after the VSWR had risen 
from a rain storm.

What I finally did was to rub silicon grease sparingly only on the threads 
of the connector (outside of the coaxial connection) and it indeed 
inhibited the water from getting into the center RF area of the connector. 
Furthermore, when water did occasionally get in, it was easy to remove and 
repair.

73,

Joe, W1JR

At 12:13 PM 6/26/00 -0700, Ken Hirschberg wrote:

>Gentlemen:  I've been following this thread for some time now.  Please 
>consider
>the following:  What is put into aluminum antenna element joints serves 2
>purposes. First, lubrication for assembly and disassembly.  Second, and most
>importantly, it protects the connection by excluding moisture and air at the
>points of contact.
>
>Contact between the pieces will occur between 2 or more points, depending on
>how the pieces are fastened.  It is unnecessary to include metal particles in
>the formulation to make a good connection.  Some of the commercial 
>formulations
>(e.g. NOALOX, Penetrox, etc.) that have been mentioned (and even used by
>reputable manufacturers) are intended for electrical wiring.  The antenna
>environment is a different, much tougher ball game.  If the carrier of these
>metal-loaded formulations happens to be silicone-based and is thick enough,
>there is little or no problem; if it is petroleum-based, it is quite likely to
>be washed away, leaving a dissimilar metals problem.  (The copper-loaded
>compounds, e.g. Penetrox B, can be really bad news)
>
>What to do:
>Simplify the problem; just use a thick silicone grease.  It has proven itself
>in very harsh environments.  BTW, it is also the goop-of-choice to put inside
>connectors such as PL-259's to exclude moisture.
>
>Where to get it:
>  Thick silicone grease is available as High-Vacuum grease, a Dow-Corning
>product, from scientific supply houses.
>
>GC (formerly General Cement) packs it in small tubes, which are available
>through electronic supply houses; Newark, Allied, etc..
>
>My company, CAL-AV Labs., supplies it in 1/4 oz. containers as part of the
>assembly kits sold with our antennas; we would be happy to sell the grease
>packs alone if you can not find them locally. (cal-av.com)
>
>It is also available at SCUBA diving shops, typically in 1/4 and 1 1/2 oz.
>packs or tubes.
>
>Sincerely,  Ken K6HPX
>
>
>
>wbh3@daimlerchrysler.com wrote:
>
> > FWIW when I built my  kt34-xa about 7 years ago, KLM supplied a little can
> > of  copper-colored paste to put on the joints.    After a move and whenn I
> > was reassembling the end units I found this paste had turned very solid and
> > seemed to be a good insulator as the resistance checks I made on each
> > element end were very high.  Don't know what KLM used but I don't think it
> > was very good stuff.
> >
> > Bill Haselmire  WX8S
> >
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