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!

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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.