Some years back, my MFJ-1788 started misbehaving. I could hear the electrical noise of the motor tuning, but the antenna would not tune. Eventually I removed it and, well, here's the problem. Look closely or click any pic for a bigger version:
Wasps nests! All over the variable capacitor and feedpoint. Here's the tuning cap again:
There was actually a nest UNDERNEATH that assembly. I found that the cap rotor part could not physically turn because a nest underneath was in the way. Once removed, it turned just fine, actually too easily, because sadly the shaft seemed to have sheared inside the motor. Although the motor runs, its output shaft does not turn. Here's the motor and control board:
Yuck. Dead wasps and crud everywhere, but nothing damaged. Now for the feedpoint:
Yuck again. Total haul of nests follows:
Yuck!
One note of interest... the cap itself gets about 3kV on it when tuning up around 40m, which is where it was stuck. This can't be a nice environment for baby wasps. Maybe this is why they abandoned nesting there around this time: my tuning attempts were zapping their nest!
New antenna motor!!
After a new motor and much cleanup, the MFJ-1788 rocks again! It's only about 10cm above the flat roof, but loads up perfectly with 1:1 SWR on most bands. That's a VHF Quadrifilar Helix antenna above it for 2m and satellite use, with an Iridium antenna on top.
To prevent the wasp problem from reoccurring, I used electrical duct seal to block off the four gaps where the loop enters the housing. I highly recommend this. You can buy electrical duct seal at places like Home Depot. It's fairly cheap and you can use what's left over to make a very effective back stop for a pellet gun target if you're into that sort of thing. I also drilled a few small holes in the bottom of the housing to make sure that any condensation can easily drain out (but not big enough for wasps to enter).
