My original 80/160m antenna has served me well since transferring here to Guam. It was configured with balanced “window line” as an inverted L on 80 and a top loaded TEE vertical on 160m. The top was at about 58ft, the highest I could go with the current mast configuration.
The problem was that the two top loading wires were not 180 degrees out from each other. They were more of a 120 degree separation, because of where the coconut tree end supports were located. This pulled the mast to one side, and the prevailing trade winds pushed it over even more. I attempted to back guy the mast, but since I had threaded the mast through the center of the tree, I could not get the support to the top and eventually the mast started to bend.
Eventually it got so bad that my kids named it the “Banantenna”.
Every year I like to try to improve the antenna system. This year, the project was obvious: replace the Banantenna.
The new mast is now taller, just under 70ft. It is much stronger. The top section is a 25ft long piece of bamboo, which is strong and plentiful. It is lashed to a section of aluminum boom, which in turn is telescoped into a 20ft piece of 2″ water pipe. The new mast is routed through the tree differently, and is much easier to put up and take down. This is important, especially during typhoon season.
Gone is the 80m inverted L and 160m TEE. The new antenna is a full 1/4 wavelength high vertical for 80m, which is top loaded for 160 with three top loading wires. The top loading wires are staggered 120 degrees and serve also to support the mast in the wind. Again, I used 450 ohm balanced “window” line. At the feed point, both wires are joined. At the far end, one simply terminates (this side is the 80m vertical), the other continues to the top support and three top loading wires (160m top loaded vertical). Essentially, I have two parallel verticals, separated by one inch (the window line). They share the same feed and radials.
The feed point has not changed. I still use a remote vacuum relay to switch a hairpin coil across the feed point when on 160m, this serves to match the low impedance 160m antenna to the 50 ohm transmitter. The impedance on 80m is high enough to be fed directly without matching.
The new antenna does seem to work better than the older version. Stateside stations seem to be hearing me better than previously on 160m.