Improving connections on 40-2CD loading coils

The Cushcraft 40-2CD and XM-240 use identical loading coils on the driven and reflector elements to help shorten the overall element length. The original design of the loading coils used a sheet metal screw to attach the wire coil to the aluminum element. Even though it is covered by heat shrink tubing, it becomes a point of failure when the sheet metal screw begins to corrode.

I recently rebuilt two 40-2CD antennas and had the need to renew the loading coil connections.

View of a corroded sheet metal screw when the heat shrink is removed
Another sheet metal screw that is in better condition

The first step is to remove the screw and clean everything up.

Element and wire cleaned

Drill a hole through the element. This will allow use of a stainless steel nut and bolt for a much more secure connection. I used a washer to help hold the wire. Also applied a dab of SS Jet-30 to improve conductivity.

New stainless nut and bolt attachment

I then used some rubber liner tape to wrap the connection point to make it as waterproof as possible.

Tape over the connection to make as waterproof as possible

I then used some 1.25″ heat shrink tubing to cover the complete loading coil.

Heatshrink tubing covering the loading coil

Simply repeat this process for each loading coil. This small effort will prevent a common failure point for the 40-2CD antenna.

Sorry I didn’t record all the part sizes that I purchased at the local hardware store, but here they are in a photo.

For reference, here is a loading coil with all of the shrink wrap tubing removed.

Loading coil with shrink wrap tubing removed