[TowerTalk] driven element center insulation

[Jim Thomson]

Date: Sat, 14 Oct 2017 14:30:52 -0400
From: Dave Sublette <k4to at arrl.net>
To: towertalk at contesting.com
Subject: [TowerTalk] driven element center insulation

<I just put up a 40 meter rotary dipole using leftover Telrex elements.  The center of the element is 1.625? O.D with a section of 1.5? O.D. tubing inside.  I had a friend turn down an Oak piece to 1.375? and inserted it to join the two halves.  I coated the Oak with epoxy to bond the two halves together and to try and keep moisture out of the wood.  I split a piece of schedule 40 PVC pipe and put it around each half, clamshell fashion, to insulate the driven element from the U-bolts used to hold it to the mounting plate.

My next project will be to build two, two element Moxon yagis for 40 meters.  I would like to use a split driven element.  Instead of Oak, I would like to find some sort of high strength insulating material in tube form to go in the center.  It would also have to be 1.375? O.D. because I am using more of the Telrex elements to build the Moxon.

What sort of material would you all recommend?  Telrex literature says they used phenolic insulation.  I?m guess there is a better material available after forty years.  I am hoping (but not very hopeful) that I won?t need stays on the elements if the center material is strong enough. 

As always, I look forward to the resulting discussion that this great group always supplies.

73,

Dave, K4TO

##  max gain systems.  https://www.mgs4u.com/fiberglass-tube-rod.htm  scroll down till u get to solid rod. 

https://www.mgs4u.com/ecommerce/product/1-12-od-round-solid-rod/   This is the biggest they make...  1.5 inch OD..and its solid fiberglass.   Available in 2-4-8 ft lengths.   4 ft is easy to ship. 

Get ur buddy  to machine .005  from  the  1.5  solid rod.   Then its  down to  1.490   
Then it will slide in like a glove... problem solved.

Jim  VE7RF