|Antenna Bonding/Surface Coating - RF Cafe Forums|
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Post subject: Antenna Bonding/Surface Coating
Posted: Fri Feb 09, 2007 2:49 pm
Joined: Thu Feb 08, 2007 7:47 pm
Location: Plano, TX
Can anyone comment on the following? After inheriting a partial design (with antennas already ordered and the tower designed by a 3rd party), I have to mount Dayton Grainger UHF omnis, pn FM10-376-2 (same as Rockwell Collins pn 013-1656-010) to an existing mounting bracket, already welded to an existing, painted steel tower. After taking the mounting bracket to bare metal, what is the best non-oxidizing/conductive coating that I can apply to the mounting bracket prior to bolting the antenna base on? Without any coating, I will have steel to aluminum. (Yes, I know.)
I can not send the bracket out to a fab shop for plating so this has to be done in situ.
Not that it makes any difference, but these antennas have the old fashioned, radial ground rods on the antenna base. And yes, I have installed a Polyphaser lightening protection system.
Any ideas and/or specific part numbers would be greatly appreciated.
Posted: Mon Feb 12, 2007 7:55 am
Joined: Fri Feb 17, 2006 12:07 pm
Location: London UK
There are 2 methods I have used both for the situation you describe and also for use on a sailboat in a sea-water environment, which had galvanised steel fittings that had passed their sell-by date.
The first, that I would recommend for the tower steel, was some paint-on so-called "dry galvanising" which is much used in farming for steel gates and such. I was given a tin that had lost its label, so I have no idea who makes it. I guess it was a very zinc-rich paint.
As a barrier between the ali tube boom and the steel tower I have used teflon ptfe tape as used in plumbing for union/joint wrapping. This is about the only barrier that has a long life under ultra-violet sunlight radiation. It is cheap and can easily be wrapped around the boom tubing. Then a galvanized clamp to the tower gives an intermediate electro-chemical voltage half-way between steel and ali. I have even used this tape as a barrier between ali and copper, with no failure during twenty years installed.