Steve -
Here's an update:
Yesterday, I received my Tennedyne T7 LPDA antenna, and looking in the
manual that came with it, they have the following statement in bold
print, and in all capital letters:
"DO NOT USE ANTI-OXIDE GREASES ON THIS ANTENNA"
On the same page, the manual says "..... and we recommend the use of a
mixture of WD40 and graphite powder, or similar material, to lubricate
each and every tubing joint surface and screw hole during assembly as
well as the end of the element being placed into the boom."
Therefore, if I follow the advice of what 99.99% of all hams are
telling me (i.e. use Pentrox or similar antioxidant) and what common
sense and the laws of physics dictate, I will be in direct violation
of the K7LXC Prime Directive! Decisions, decisions.......
73 Rick WN3T
______________________________ Reply Separator _________________________________
Subject: Re: [TowerTalk] Penetrox vs WD40/graphite
Author: K7LXC <K7LXC@aol.com> at osc-link
To: <towertalk@contesting.com>
Date: 4/18/98 1:05 PM
In a message dated 98-04-16 08:30:20 EDT, dessel.rick@Orbital.COM writes:
> I have been getting some confusing advice for corrosion prevention
> during the assembly of the antenna.
>
> Several hams have told me to be sure and put a coating of "Penetrox"
> or "OX-guard" on every electrical connection while assembling the
> antenna. The antenna is made of 6061-T6 aluminum.
>
> But in talking with Tennadyne, they say DO NOT use Penetrox or similar
> compound, if you do, the antenna will not function properly. They
> recommend using a combination of WD40 and "lock" graphite. They have
> even put this in writing in the manual.
>
> So who is correct? If I use Penetrox, it will be in violation of the
> manufacturer's recommendations, and may even void the warranty.
>
> By the way, my QTH is Northern Virginia near Washington, DC, so I am
> not near a salt water environment.
>
> Also, to add a little more confusion to the picture, according to the
> Galvanic Series Chart for dissimilar metals, Graphite is on one end,
> and Aluminum is on the other, which means those two materials are
> highly corrosive together!
I don't know why Tennadyne would recommend that you NOT use an
antioxidant. Any electrical connection left exposed to the weather SHOULD have
antioxidant applied.
Typical antioxidants such as Penetrox, NoAlOx, etc. are composed of two
materials. First there are lots of very small particles of materials such as
zinc or copper. The second part is the vehicle which is the 'grease' carrier
of the particles. The carrier is non-conductive. What happens is that when you
tighten the connection, the compression forces the little particles to
penetrate the oxidized top layer. Since there are lots of these particles, you
get lots of good electrical connections. And since the grease covers the
metal, it prevents oxygen from getting in and further corroding (oxidizing)
the joint. Most commercial antioxidants are to be used in copper to copper,
aluminum to aluminum and aluminum to copper connections - just the thing for
antennas and ground connections.
If you've ever taken a "mature" yagi apart (if you could!), you'll see
lots of white aluminum oxide where the elements overlap. Use of an antioxidant
will minimize this problem. Yes, you should use it on antennas. I'll contact
the manufacturer to see if we're violating the LXC Prime Directive of "doing
what the manufacturer says". Perhaps this'll be like the recent US Towers vs.
cable lubricant situation where the manufactuer actually changed their
recommended policy. Their recommended use of WD-40 and graphite is even more
puzzling.
Cheers, Steve K7LXC
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