Antenna...solve one problem only to create another.

 The antenna I have is the Hustler 4BTV, and I have owned it for about four years. I had been noticing that after a couple of days of rain, the SWR on 15 meters would increase.As the weather warmed up, the problem disappeared. My suspicion was that water was making its way into the 15-meter trap and causing the SWR issues.

I waited for a forecast of a few nice, dry days before taking the antenna down for inspection. The first thing I noticed was that I had accidentally covered the drainage slots at the bottom of each trap with electrical tape. If water was getting into the traps, those slots were intended to let it drain out. My first course of action was to remove the tape from all three traps.

Tape removed from drainage slots 

I started with the 20-meter trap, then moved on to the troublesome 15-meter trap. As soon as I removed the tape from the 15-meter trap, a small amount of water drained out. I then removed the tape from the 10-meter trap, and like the 20-meter trap, no water came out.

Each trap has a plastic cap at the top that helps keep water out while also insulating the trap tube from the center antenna element. This seemed like the most likely place for water to enter the trap, so I decided to disassemble the 15m trap for a closer inspection.

Before taking anything apart, I carefully marked the position of the tubing so I could reassemble it in nearly the exact same location. My hope was that this would keep the antenna's SWR very close to where they had been. See above drainage pic for position marking in red. 

After removing the 15-meter trap from the antenna, I took off the plastic cap and inspected it closely. I couldn't find any visible damage, but I know that water can find its way through even the smallest of gaps. That alone could have been enough to cause the SWR problems I was seeing.

Outer tubing showing water drops

 

 

 

 

 

 

With the cap removed, I looked inside the trap and found several small water droplets. I then removed the outer trap tubing so I could inspect the trap winding and all of the electrical connections.

Fortunately, everything inside the trap was in excellent condition. The winding and all of the connections looked perfect, which reinforced my belief that moisture—not corrosion or a failed connection—was the source of the problem.

After thoroughly drying all of the parts, I noticed the original bead of silicone that had been applied during manufacturing. When I first tuned the antenna after purchasing it, I had to slide the 15-meter trap's outer tube to adjust its resonant frequency. My guess is that this movement disturbed the original silicone seal. If so, it was probably only a matter of time before water found its way inside. I was actually surprised it took four years for the problem to appear.

15m trap condition

When I reassembled the 15-meter trap, I applied non-acetic, neutral-cure silicone around the plastic trap cap to restore the weather seal. While researching the best product to use, I learned that not all silicone sealants are the same. Silicone that smells like vinegar releases acetic acid while curing, which can promote corrosion on aluminum. I certainly didn't want to solve one problem only to create another.

The product I chose was GE Silicone II, which is a neutral-cure silicone and safe for use on aluminum. I happened to have an older tube on hand, but I noticed the silicone had turned yellow.  I never realized that silicone could age over time so I purchased a new tube of silicone.

With the trap reassembled, it was time to tape the joints where the antenna sections fit together. While I'm not an expert on silicone sealants, I am very familiar with electrical tape after spending my career as an electrician. Not all electrical tapes are created equal. For this project, I chose 3M Scotch Super 33+, a premium tape well known for its excellent UV resistance, flexibility, and long-term outdoor durability. Rather than list all of its specifications here, you can simply click HERE to learn more about it. 

With the antenna back in the air, I went inside to check its performance. The results on 40, 20, and 10 meters were exactly as expected. Unfortunately, I had created an entirely new problem on 15 meters!

I had solved one issue, only to create another. Fortunately, I have almost solved this new problem. In my next post, I'll explain what happened and how I fixed it.