After some more investigation of my XM240 water problem, here are my
findings:
1. Water is allowed into the elements around the screws used to attach
the loading-hat.
2. I dissembled the elements and found water in the joint between the
telescoping sections. The joints were heavily corroded after only 8
weeks outside. This probably doesn’t help the electrical contact.
Apparently water is able to wick its way through this joint.
3. The rubber plugs on the ends of the elements and boom serve to hold
the water inside.
4. The loading coils are wound on tubes, not solid rods. These tubes
will fill with water. Although not measured, the performance with
loading tubes filled with water has to be very poor. The loading coil
wires are attached with a self-tapping screw. If the element is rotated
so that this screw is on the bottom of the element, the end of this
screw can be in standing water.
5. There are no weep holes to remove water from the elements or boom.
There are two weep holes in the housing for the balun.
Conclusion: The manufacturer has overlooked some basic requirements,
needed to weather proof this antenna.
What I did:
1. Sealed the screw holes at the loading-hat with duct seal.
2. Applied Noalox to all joints to improve the electrical connection,
reduce corrosion, and provide some degree of protection against water
intrusion into the joint.
3. Removed all rubber plugs and filled the ends of the tubes with
pieces from a plastic pot scrubber. I tested it and water flows freely
through this, and it will keep insects out. A small glob of glue was
applied to the inside top of the boom to help hold the large pieces
inside the boom.
4. I drilled weep holes on either side of the loading coils to try to
keep water out of these coils.
5. Applied duct seal to all connections associated with the balun.
6. W4ZW says that the XM240 is notorious for loosing the small end
segments of the elements. He put a screw through these segments to hold
them in place. I will do this also, as soon as I get some stainless
steel screws.
Thanks to all everyone who replied. As usual, a lot of good suggestions.
Jerry, K4SAV
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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