There is a definite dielectric effect for slipping an antenna inside a PVC pipe. Here are a couple of antennas that I build to insert inside PVC and both have to be final tuned while inserted inside the support pipe.
http://sbarcnm.org/forum/index.php?topic=83.0 http://sbarcnm.org/forum/index.php?topic=58.0 I built one version of the first one listed to slip inside a fiberglass radome from a defunct commercial antenna using RG-213 and one half inch copper tubing for the sleeves. I had to use a shorted matching stub to get a decent SWR from this setup. 73 - Jim W5ZIT --- On Wed, 8/12/09, AJ <aj.grant...@gmail.com> wrote: From: AJ <aj.grant...@gmail.com> Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles To: Repeater-Builder@yahoogroups.com Date: Wednesday, August 12, 2009, 10:05 AM Does really PVC absorb or RF or just act as a dielectric? The reason I ask is I'm looking at encasing an antenna project for the sake of weatherproofing and PVC would fit the bill rather easily. 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:49 AM, AA8K73 GMail <aa8...@gmail. com> wrote: AJ, if you replace the steel mast with a fiberglass one, won't you still have the metallic feed line there? Doesn't PVC absorb RF? 73, Mike AJ wrote: On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR
