[TowerTalk] Protecting Aluminum Antennas

[Roger (K8RI) on TT]

Observability:

I live on the extended center line of a 3800' paved runway, just inside 
of the Final App[roach Fix ( FAF) for the GPS06 instrument approach.  
Instrument approaches are + 100 feet and minus zero, but students often 
fail that minus 100 as do rated pilots on rare occasion.  Also, the 
county sprays  twice a year .  Those plane actually alter course for my 
antennas. Camouflage could prove very expensive.

I try to make visiting the pilots doing the spraying before they start, 
to make sure they are aware of the antennas.
As I no longer fly, I'm not at the airport very often.From a pilot's 
perspective,towers and antennas are almost invisible from the air. Even 
the red and whit commercial towers.  At low altitude it's even worse.
We can go to just shy of 200 feet without lighting, nor painting.  I 
don't know of any ham tower being hit, but I do know of meteorological 
towers that have. That proved to be very expensive.  It's just a matter 
of time.

I only have one neighbor who is difficult.  No discrimination, that 
neighbor hates all of us, so when the new antennas (new to me), they are 
all used I expect interference complaints before I ever use them.

I've used a lot of the gold Alodine.  I didn't know there was a clear 
version.  A do-it-yourself Alodine project can be quite tedious.  It's 
akin to using a ScotchBrite pad to clean and polish the entire antenna.  
It's not hard work, just repetitive and tedious. I don't know of any 
commercial places around here that do it.

73

Roger (K8RI)



On 3/21/2016 Monday 1:22 PM, Gary Johnson wrote:
> An effective clear anti-corrosion coating for aluminum is class 3 chemfilm, a.k.a. Alodine 1500, which are all names for a particular chromate conversion coating. You more often see class 1, which is the familiar gold color. The main difference is that class 3 is guaranteed to be conductive whereas class 1 is nominally non-conducctive, though you can scratch your way through it fairly easily. Both offer excellent anti-corrosion performance, though class 1 is somewhat better. We always specify the clear, conductive class 3 for enclosures featuring EMI/RFI gaskets, where 100% shield continuity is required. Bigger plating shops could probably handle long tubes of a Yagi and the process normally isn’t too expensive. You can do it yourself on a small scale, too. So with class 3 chemfilm, you keep your shiny aluminum while maintaining electrical connections even if you don’t attempt to abrade it away.
>
> While a clear *anodize* would be the ultimate in protection, the last thing I’d want to be stuck doing is grinding away at it with silicon carbide paper for many square feet of tubing in order to guarantee large-area connectivity. Sorry, it’s NOT that easy by manual processes. You could have the parts masked during plating, however.
>
> As for low observability, that’s my goal here in my CC&R area, so I paint my verticals. I use NATO non-spectral grey… Well, not the official paint, but grey primer makes a darned good match to the fuselage of any military aircraft that I’ve worked around. Non-spectral = flat = no glints in the sun. If I miss a small spot, it shows up like a beacon in the sun! Light grey has generally proven best against the “average” sky, thus its wide military use. I prep the aluminum as follows: 1) buff with fine steel wool, especially if it’s got any signs of dirt or corrosion 2) degrease with chlorinated solvent 3) wipe down with Aluminum Prep 79 (available from Aircraft Spruce; it’s basically a phosphoric acid solution with surfactants; it activates the surface)  3) rinse with water (you should see few water breaks) and let dry 5) paint with Rust-Oleum pro primer #7582838.  Some of it has been up about 5 years and it’s good as new upon close inspection. Haven’t been caught by the neighborhood Nazis. Yet.
>
> Gary, NA6O
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk


-- 

73

Roger (K8RI)



---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus