Recently the 145.25 repeater in Boise Idaho was experiencing quite a bit of noise resembling crackling when re-transmitting a signal. Of course it was worse when more than normal windy conditions existed. 

Checking all of the easy to get to items didn't cure the problem, go figure! Although we did find a couple connectors that needed some attention, they were not the major contributing failure. So removal of the antenna was in order. That's where the problems were. After about five years of operation the Comet GP-9 had failed.

   
Fig. 1.                   Fig. 2.                  Fig. 3.

Figure one shows the mid section of the antenna where the failure occurred. Figure two is the culprit! A weak solder connection finally separated.  Although still mechanically connected, high winds would make and break the connection thus creating the noise. Figure three shows the repaired connection, I flooded the joint with solder, no weak connection this time! The foam chunks are used to cushion and center the element in the fiberglass housing. 

   
Fig. 4                   Fig. 5.                 Fig. 6.

Another interesting malfunction was the very top of the antenna. Figure four shows the extreme discoloration of the brass tube. Figure five shows the broken corroded parts. Figure six shows the upper half of the top element. Combine figures 4, 5 & 6 and they would make one 18 3/8 inch long top element!

We inspected the fiberglass housing and there were no breaks, cracks or holes. No water could get in. We figure that the glue used to secure the foam chunks and or the top housing cap, had out-gassed while curing and began the corrosion process. If it was water it would have been at the bottom of the antenna, not the top!

================================================================================================================================

Second Failure, spring 2008...

Near as I can tell the antenna was subjected to a near lighting strike. The four 5.6pf caps were fried and the foam insulation burned. Due to the cap failure only the lower 1/3 of the antenna was actually radiating. Replacing the caps and also replacing the upper 18 1/2 inches of very badly burned/corroded brass element put this antenna back on the air.

Base capacitor configuration...there is a 3 pf cap in series with a 3.5 pf cap, the one on top of the coil is an 11 pf.

Third failure, spring 2009...

Well mother nature got us again! This time the strike was allot more intense, as you can see from all of the pictures. 

This picture is of the end of the upper section where the strike actually hit. It didn't shorten the length at all but did melt the end!

This is the burned through entry point of the strike. About 3 3/4 inches from the antenna top. As you can see, it burned a hole through the fiberglass this time and melted the element end, shown in the prior pic.

Again the caps were destroyed. This is the upper section.

This is the mid section. The foam pieces were burned very bad this time, some actually were gone. There was water in them when I took the antenna apart. Could have gotten in only through that burned in pin hole!

No problems were found any further down than this point. The lower section and feed point circuit was fine.

I cleaned up the boards as best as possible with a small stainless steel brush and replaced the caps. The antenna tuned up perfectly once again!

This antenna will not be going back into repeater service. We obtained a commercial four bay folded dipole type to replace it.

Other fixes were the total disassembling of the hard line connectors. Over the course of time, they too had become corroded and contaminated. Although there were no discernable water entry points as the sealing looked very good, but somehow it became very corroded. The type of connector was that which used a silver plated sleeve which just slid over the hard line inner conductor. This is where the major problem was found. That inner conductor was turning black, didn't get any pictures of it, sorry. In any case, cleaning it up and soldering that sleeve to it, cured the massive crackling that had also been a problem.

The system works HOT again! Great transmit and receive capabilities once again! 

The only problem left is mother nature. Storms come through occasionally and create a tremendous static noise level that disrupts the repeater use. Even with the grounded antenna design in use now, that static sure is a pain!