[TowerTalk] Recommendations re. Comet GP-15 6-2-440 Vertical

[Mark .]

Dave wrote:
<< I have just acquired a used Comet GP-15 fiberglass covered vertical.
This neat antenna covers 6, 2 and 440.

I'm looking for recommendations as to preferred mounting height,
concerns about proximity to other antennas, and anything I might
do to enhance longevity.

The current plan is to clean the radials with a green pad and spray
them with some sort of protective coating.  What should I use?  What
should I avoid?

My first thought is to mount it on the very top of the Rohn 45, above
the Force 12 C3SS, with the base at about 80 feet -- about 2 feet
above the C3SS.  Sound OK?- - Thanks! & 73, DavidC  K1YP in Hudson, FL >>

Hello Dave,
I put up a fiberglass radome, 2m/440 vertical on my tower. I side-mounted it 
using a mount made by IIx equipment. I tried to think about longetivity (low 
maintenance) as well before the installation.
As far as I can tell from my readings, these types of antennas have 4 main 
modes of failure:

1) Spectacular disintegration from being struck by lightning as the tallest 
object on a tower.

2) Fatigue failure of the fiberglass and foam spacers for the radiating 
elements inside, due to flexing in the wind.

3) Breakdown of the fiberglass from years of UV exposure.

4) Water leaking to inside of radome.

My approach to longetivity, which addressed all of these:

1) I side-mounted the antenna on the tower (approx. 3 feet away), with the 
top about even with the top plate of the tower. I put a lightning rod (air 
terminal) on the top of the mast (tallest object, above all antennas) as a 
preferred path for lightning. This compromises ultimate performance and 
height of the antenna somewhat, but I predict it will greatly promote a long 
life. It performs quite well side-mounted.
If I had installed the antenna on the mast, the top tip of it would be the 
tallest object for miles, and a good 25-30 feet above the treetops. If you 
really want to have a multiband fiberglass VHF/UHF antenna on top, I believe 
you should plan on climbing and replacing it at some point over the years. 
It's hard to tell how long it will go before lightning, static, or a 
streamer gets it, especially the multiband units, which use tiny coupling 
capacitors in the radiating elements inside.

2) I installed a stabilizer arm up about 2/3 on the antenna. I made an arm 
from a piece of 1" PVC, spray-painted light grey, to protect it from the 
sun. This is possible, of course, only if you side-mount the antenna, and 
eliminates almost all of the fatigue-producing flex.

3) I wrapped each joint of the radome with Scotch Super-33, UV-resistant 
electrical tape. Next, I covered the entire antenna with a spiral wrap 
(bottom-to-top) of the same, as a sacrificial sun/UV blocking layer.

Dave, good luck with your project and hope these ideas were helpful.

regards,

--...MARK_N1LO...--
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