TheRadioBoard

I would like to home-brew a center-insulator for an outdoor 40m dipole antenna. It would include holes for dipole attachment, coax strain-relief, and a support line. A piece of sheet material such as phenolic, delrin, or polycarbonate seems ideal except there are issues such as weathering, UV degradation, wather absorption, etc. Any comments, suggestions?

Thanks.
73, Roger

Hi roger,

I dont know about "plexiglass" but have thought about trying it.

PVC as in Plumbing pipe handles the weather quite well.

A warning about plastic tie wraps"wire ties", some are good in weather and some are not.

I dont know what kind of plastic the cheap ones are made of but after being exposed to cold weather they get brittle. The nylon ones are better in this regard.

Also some plastics break down in sunlight.

73
kb0lxy - Eric

Hi Roger.

I've used 1/4" plexiglass (got it at ACE Hardware) to make folded dipole center insulators. Stayed up 6 years with no problems. Only took it down because I wanted to redesign it.

And the plastic wire ties - look on the package for "UV Resistant".

73, Dan

You can make nice centre insulators/feedline supports from a plasdtic cutting board available at most hardware and/or houseware stores. Most are HDPE and stand up well to sunlight and temperature extremes.
They cut and drill nicely with regular woodworking tools. I've got several that have been up for over a decade and are still in fine shape. Best of all, they are inexpensive!

73, J.B., VE3EAR

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To be where I am, I had to leave where I was!

Use PVC conduit it is UV resistant (gray)

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Mark

Hi Roger, before I switched to using all full wave delta loop wire antennas, I used to make my dipoles center insulators out of PVC "T" connectors. You can put an eye bolt in the top center and screws in each end for strain reliefs. Works real well. Good luck with your project!

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73, Bill NT9K
http://www.nt9k.com

If you’re the smartest one in your group, your group is too small..

Thank you Gentlemen!

Excellent suggestions from all of you!!

Roger

Here's a photo of the end result...



Most projects let you pick two of the following... Fast, Good, or Cheap! This was one of those rare cases where I got all three!

I modified a W2AU end-insulator to function as a center insulator for a wire dipole. This choice took care of the weathering, physical stength, and voltage breakdown issues. Two extra holes were drilled in the insulator for a support loop made from 1/8" copper tubing. The two center fins were machined down to provide space to loop and secure the RG-8X coax line.

Immediately below the insulator is a current-mode balun made from a string of ferrite beads (Palomar Engineers BA-58 Balun Kit).

73, Roger