Wow…two blog posts in two days….!

Yesterday found us at K4MK’s Lexington NC home, where we were finally getting to install a replacement antenna for the taken-down 2L 80M Create beam. Having gotten tired of the maintenance issues dictated by the large beam, Kent decided he would try an 80M four square, since the tower was 130 feet tall & would easily allow its installation. But we were hampered or sidetrack when a huge windstorm blew down some relatively full growth trees on one of the guys. Luckily, the EHS did not break, & luckily there was nothing else on the tower, so there was no damage. Just a whole of clean up work, including replacing one guy anchor which was pulled out of position. Anyway, Kent finally got caught up with that, & the weather finally cooperated with my schedule, so away we went.

I built up a four square “support” system, using a cubical quad hub or spider, to mount the fiberglass support arms on (encased in gray PVC), & supported by a Phillystran truss setup. This not only gets the dipoles up and away from the tower, it allows for a slightly less acute angle to the ground, which I think helps clean up the pattern a bit.

Here are a couple pictures to give you some idea of the construction:

002 003

The aluminum mast (6061-T6 alloy) is 12 feet long, & at the top is a steel ring holding four turnbuckles, connected to the Phillystran truss cables. The bottom of the mast is held in place by a Hy-Gain rotator “mast mount” bracket, which I’ve used numerous times to do jobs like this (including mounting stingers inside towers to be used as verticals).

The install went surprisingly fast (Joe came up to hold the spreader arms in place as I installed the clamps), then we went down & began getting the dipoles in place & running feedlines to the COMTEK phasing box. (This work took far longer than anticipated, & we basically ran out of daylight.)  But the initial testing, even without the dipoles being fully extended, indicate a 3800 kHz resonance, with virtually no dumped power.

When the weather finally improves, Kent will get some more trees out of the way & the dipoles pulled out further, & likely have a fine working four square.

stay tuned…

This entry was posted in Blog. Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *