>
>Hello,
>Since starting to use my "big boy" amp, I have had more antenna problems
>than in all my 40 years + of ham radio.
>Examples:
>1. Those cheap black plastic insulators commonly sold at hamfests melt.
>The result is the antenna falls.
Amen
>
>2. A small tree branch (1/4" dia.) fell from a tree and was hanging from
>the end of the antenna (I just happened to notice this). The first time I
>put power to the antenna, the 12ga stranded copper wire melted at that
>point and the antenna fell down. I found the small branch on the ground
>and it showed signs of having been on fire.
>3. The latest happening is the strangest (I swear it is true). After
>tuning up the amp into a dummy load, I switched to the antenna to fine
>tune the amp settings. While fine tuning, everything looked normal then
>all of a sudden, all the amp meters went wild. My first thought was "damn,
>one of those paracites, how will I ever get rid of it". Then I went back
>to the dummy load, and every thing was back to normal. I immediately went
>out into the yard and found the antenna on the ground. The 12" by 1"
>ceramic end insulator was broken at the antenna end. I could not visually
>find any defects in the insulator at the failure point.
>
>Is all this being caused by corona effects?
my guess is yes.
>What could be the max voltage
>at the antenna ends?
Depends on wire gauge and watts.
>Copperweld appears to be the only way to go for wire,
If one provides support for the center of the dipole, TW wire is strong
enough.
>but what should I be using for end insulators?
>Any insight would be greatly appreciated.
>
After too many meltdowns/fires, I wound up using 1/8" Teflon sheet stock
for the end insulator. The length needs to be about 18" and the width
about 1.5 inchs. A leather punch works ok for making holes. To minimize
corona, solder a 6" diameter loop of copperweld at the end of the
antenna. // The weird thing about corona is that most of the melting
does not occur at the end of antenna wire. It happens several inches
beyond the end.
cheers, Bruce
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|