The Hustler 4BTV
For most of my HF traffic, I use a Hustler 4BTV antenna. The antenna is a vertical trap antenna capable of working the 40, 30, 20, 15, and 10-meter bands without using a tuner.
I installed this antenna five years ago, and it has always worked fine, with a reasonable SWR on all the bands. Before I took it down, the only band with an SWR around 3:1 was the 40-meter band. But the radio's tuner compensated for it without difficulty.
For the last few months, the SWR on all the bands has been slowly creeping up. For example, over the summer, the SWR on the 20-meter band went from 1.2:1 to 2:1.
This problem motivated me to disassemble the antenna. Clean all the elements to make sure the electrical contacts are good. Clean and re-adjust the traps. Ensure there is no corrosion, loose connection, or bug nesting in the traps.
After thoroughly cleaning, I reassembled the antenna. I have re-adjusting the traps to the manufacturer's specifications. I have replaced all the worn-off clamps and used conductive grease everywhere two pieces of aluminum come in contact. After a while, oxide builds up on the aluminum, seising the different parts, and making further adjustments impossible.
While cleaning all the parts, I discovered that the connection between the antenna element and the SO239 was held by only one thread of wire and the shrink tubbing. As you can see in the picture, that weak connection was due to a cold solder joint. This problem was probably why my SWR has been going up on all the bands lately.
The antenna is now operational again. As you can see in the following graphs, the antenna has a good SWR on all the bands. The 40 meters is still a bit high, but it is better than before the cleaning.
Finally, this graph represents the return loss and VSWR of the antenna from the 40-meter to the 10-meter band.
As you can see, the antenna is resonant on the 40, 30, 20, 15, and 10-meter bands.