I like the conduit bodies for the center but the weak link is the shorting points on each leg. I am using epoxy and heat shrink on this antenna and yet I think it may not be enough. If this joint fails the thought occurred to me to use a piece of PVC pipe over the shorting point and fill it with epoxy. The down fall of this would be the added cost in materials and more epoxy.
This is the center made from a conduit body with a chassis connector installed and a stainless eye bolt, washers, and nuts for supporting the antenna. The RG-6 has an aluminum shield so I have used crimp eyelets to make the connections to the coaxial connector. The eyelet going to the center is soldered in place.
Here I have the body filled with 3 oz of 5 minute epoxy, this strengthens the antenna and adds weather resistance.
Here I have one end of the coax stripped back ready for the shield to be twisted around the center conductor and crimped on.
I used a piece of masking tape to mark where the end of the heat shrink tubing needed to be.
I purchased a smaller tube of epoxy with the mixing tip so I could "inject" epoxy under the heat shrink and around the crimp connector that is creating the shorting point.
This is the above connection after "injecting" the epoxy and shrinking the tubing.
This is the center after the epoxy is set and a coat of paint applied.
I wrap the connector with masking tape to keep the paint off the threads.
I put this antenna up on my 21 foot telephone pole to test it and it has 1.5:1 SWR or lower across the entire band. The shorting points seem to be solid. (I put plenty of tension on it with the ropes on the ends.) Although the joints seemed strong enough, I am going to use a sleeve and fill that with epoxy to seal and strengthen the next one I build, most likely for 40m or 20m.
As a side note, the 75m bazooka made with RG-213 is still going strong!
if you want to make the joints stronger especially where the coax meets the single wire then take steel wire and make a stress link across the 2 twisting it over the insulation on both wires. before tightening the second twist push the joint together into a little droop then tighten. this will make the steel wire take the stress instead of the connection. just something to try :-)
ReplyDeleteIts Ironic that you would crimp the wire as opposed to Soldering the center conductor since you went through so much trouble to epoxy under the heat shrink
ReplyDeleteThat point is crimped because the cable I used has aluminum for the shield. Aluminum does not solder, so I chose a mechanical method of attachment.
ReplyDelete