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Here's a problem: you buy a fancy new vertical for a fair bit of coin, but there's no coax connector on the thing. There are just screw terminals.

enter image description here

You need to attach coax to it, but in such a way that the coax termination is protected from the elements so you don't get water wicking into the shield. How do you accomplish that?

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    $\begingroup$ I've never seen a vertical with screw terminals - do you have a picture? I'm not sure if latex caulk would corrode the braid or eat the sheath, but its the first thing thing that comes to mind. Or epoxy glue, more permanent. $\endgroup$ – Ron J. KD2EQS Jun 7 '14 at 13:44
  • $\begingroup$ After further thought, the screw terminals probably mean a ladderline (300 or 450 ohm) is the intended feedline. $\endgroup$ – Ron J. KD2EQS Jun 8 '14 at 13:10
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    $\begingroup$ @RonJ.KD2EQS I'm quite certain that's not the case. $\endgroup$ – Phil Frost - W8II Jun 8 '14 at 20:19
  • $\begingroup$ What does the manufacturer recommend? $\endgroup$ – SDsolar May 13 '17 at 22:19
  • $\begingroup$ @SDsolar pulling the center through the braid, then putting ring lugs on each, then gobbing "sealant" over the whole thing. Which works great, until water wicks through the braid and past the sealant. $\endgroup$ – Phil Frost - W8II May 15 '17 at 12:25
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What I have done once for a dipole was use a SO-239 panel receptacle with a solder cup to make my own "coax to two wire" adapter. For example, I used something like this part from Mouser. That way, I had a whole piece of coax running to the antenna that could be weatherproofed, and then an exposed section that just had regular wire soldered to the receptacle.

picture of a panel-mounted coax connector

I think I would try to fasten the "panel" side to the ground terminal somehow, and then run wire from the center conductor to the "positive" terminal of the antenna. The center insulator would need to be weatherproofed as well, but it should be a lot easier than weatherproofing coax braid.

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  • $\begingroup$ i can haz pictures? $\endgroup$ – Phil Frost - W8II Jun 9 '14 at 21:14
  • $\begingroup$ @PhilFrost Sorry, it was a long time ago. I basically used a piece of plexiglass as a center insulator for a dipole. At that site, we could leave the antenna up, but not the feedline. $\endgroup$ – W5VO Jun 9 '14 at 22:14
  • $\begingroup$ This is what my VERY portable dipoles used. 75 ohm RG-59 and tiny wire on a spool that could fit in my pocket, with this connector on the outside of the spool. We were a checkpoint for the Yukon 800 boat race, way out in Ruby, Alaska (near Galena), and had to wear bee netting because of the mosquitos. We unspooled the thing and used a bow to shoot monofilament up through the trees, and strung up a 75-meter dipole and had a rock-solid connection on 3905. At night we could go the 350 mile distance, but daytime we had others who could relay for us. And it all started with an SO-239. $\endgroup$ – SDsolar May 13 '17 at 22:26
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This looks a lot like what we had at our commercial radiotelephone stations in the days before cell towers.

We built small metal boxes for the feeds to enclose it.

Our feedlines were thick coax. RG-11, I believe, connected directly to the screw terminal and the shield to the mounting bracket which was connected to the radials.

Weather sealing was done at the connection with that terrible tar-like black tape on the inside, then we had silicone all around the small box that fit right around the connection point.

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After you jerry-rig your coaxial connectors in whatever way you choose you want to use a product called Coax Seal which is available from Amazon here. Even though this product presents itself like a roll of thick black electrical tape it is not necessarily used like that. You wrap up the connection to be sealed as best you can and then using your thumbs and fingers you mold the seal into and around the unusual places and form something tight.

I have used this product with a whole slew of different types of situations and some worse configurations (for sealing) than shown in your photo. The key though is applying enough of the seal and then molding it to fit the piece being sealed as well as to satisfy your fitness to the purpose.

Long lasting. I use this seal on coaxial connectors that run to my mobile antenna and under the body of my truck and the seal was just as effective after 10 years as it was the day I applied it.

One thing -- it is a bear to take off unless you use some thinners and other solvents to help dissolve it.

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    $\begingroup$ I've seen broadcast engineers wrap the connection with ordinary electrical tape first, before applying a mastic like this. They call it the "courtesy wrap". $\endgroup$ – Phil Frost - W8II May 15 '17 at 12:21
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Where practical I will pot the connection up permanently in resin. Auto body filler works well enough and can be purchased in gallon quantities and up. Just be mindful of the heat buildup that occurs with large cross sections and plan accordingly.

Once I built a N4UJW 2m/440 dipole using this method. The center feedpoint is potted using the above instead of hot glue. In vertical it still reaches stations 40mi distant after 4 years at modest PEP.

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