Thursday, December 22, 2016
Respect Your Antenna Insulators!
OK, so I got a little re-education on something I had forgotten tonight. Had a little time before dark to tweak on the 40m elements of my hexpole antenna (had to give it a snazzy name, it's just 3 dipole/inverted V antennas fed from the same feedline). Anyway, the 40m portions have been acting goofy and tougher than usual to tune.
The 40m legs needed to be lengthened a bit to move the resonant freq down a little. I made a pigtail, and attached it to the ends of the antenna. I didn't want it just hanging down (not that it matters), so I pulled it across the end insulators, and zip tied it to the paracord on the other side of the insulator. The paracord was a little damp, but didn't give it any thought. It's a synthetic cord, so no biggie, right?
I went in the shack, and checked it at 100w, and found the SWR dip to be about where I wanted it. I kicked on the amp, and loaded it up to 1,499 watts, and noticed the reflected powder to be a little quirky. Suddenly, everything went nuts and I shut it down. I walked out, looked up, and found one of ends of the 40m antenna to be hanging down by the tower, and the guy cord to be on the ground.
Duh, the high voltage points on that type of antenna are at the ends. The damp paracord, was not a good insulator. Arcing at the ends of the 40m elements had literally burned the cord off, flush with the ends of the antenna. I repaired the cord connections and let the ends of the tuning pigtail hang down (not across and against the paracord). All is well.
Gives new meaning to putting some "fire in the wire" :-)