[TowerTalk] How to waterproof a split coax feed to yagi?

[Ian White GM3SEK]

>To feed my Force 12 HF yagis, I plan to wind my own coax baluns (8 
>turns of coax, 8" diameter - sound reasonable?), and would like to 
>simply spilt the LMR400 coax feedline, with the ground braid going to 
>one side of the dipole element, and the center conductor to the other.
>
Someone else is sure to comment on the choke baluns...

>I am wondering what is the best way to **waterproof** the split coax. 
>Is there some type of goop or sealant that has excellent waterproofing 
>and UV resistance, that I can use to keep water from seeping into the 
>coax? I would welcome any thoughts and sources....neither Home Depot or 
>Lowes had anything that seemed like it would work.

Betcha they did: hot melt glue.

Ordinary translucent glue sticks (not the yellow or white kind) are 
basically polypropylene, which is an excellent RF insulator. Used in a 
glue gun, it's also an excellent water sealant - it sticks equally well 
to metals and all common plastics [1].

We don't have much UV around here; but it has far better UV resistance 
than epoxies or any of the soft transparent glues that come in a tube. 
I've had some samples outside for approaching ten years now, and apart 
from slight dulling of the surface they're as good as ever.

What we DO have is plenty of rain, sea mist and wind-borne salt. The 
translucent glue makes it easy to check the condition of the connections 
without unsealing them. In spite of doing all the wrong things with 
dissimilar metals, nothing shows the least trace of corrosion.

It can also be peeled off smooth surfaces (with some effort, because it 
does stick well) to leave a clean surface.

One thing hot melt glue doesn't do well is to seal onto large hunks of 
cold metal, because it chills immediately on contact. That can sometimes 
be fixed by warming the metalwork with a hot air gun before applying the 
glue.


[1] Warning: hot glue also sticks to skin, and can give very nasty burns 
like boiling jam.


-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek