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[Towertalk] Balun Location (more)

To: <towertalk@contesting.com>
Subject: [Towertalk] Balun Location (more)
From: k4oj@tampabay.rr.com (k4oj)
Date: Thu, 10 Oct 2002 23:31:53 -0400
...perhaps I am assuming too much again -

For me, the feed point attachment is on the underside of a yagi driven 
element and has the pigtails drooping away from the element towards the 
ground... this mini drip loop THEN  turns up hill to where the outer 
shield and center insulated wire diverge into the Y....so...the Y is on 
the underside of the yagi as well and occurs before the coax is attached 
to the boom.... for water to get into the coax there it would first have 
to go up the little hill and then get past the taoe and goop at the "Y".

Being a Floridian for almost 25 years now I can say I have seen driving 
rain but not of this calibre! Adopting the PL259 type dipole center 
insulator once again means you have that failure point of the PL259 to 
the Female dipole barrel...

Technique:

FWIW - I pass the center conductor through a hole in the shield made by 
parting the weave of the shield and then sticking an awl (ice pick) so 
that it gets in between the insulated center conductor and all of the 
shield.  You have to pull hard to persuade the double width of center 
conductor to pass through the parted weave...but once you have done that 
tugging on the end of the shield results in it tightening back up and 
re-assuming its woven pattern.  Now is when you start waterproofing.

Wrap tape about the black outer covering of the coax and walk that wrap 
up to the point where the shield and center go their searate ways.  Make 
a few turns around the shield only then head back down the coax until 
you are back on the full thickness coax - cut the tape.

Apply some goop - I like either liquid electrical tape or the dip it and 
make yourself grips for your pliers stuff...

Let dry - go away for a day.

Now do a similar taping procedure except when you get to the "Y" take 
the insulted center conductor route...and then back onto the full coax.

Goop it up at the "Y:" and let it dry overnight.

Make a straight line pass of tape which runs the same direction as the 
coax itself - along the length of the coax starting on the last wrap of 
tape...when you come to the "Y" go through the middle of the "Y" and 
back down the opposite of the coax.  Coat the whole thing with a liberal 
dose of Scotchkote and let sit.

Finally wrap the whole mess in one more layer of tape, use the wrapping 
direction which renders the tape shedding water onto the tape - not the 
seam - of the layer below - this tape is predominately to shield the 
Scotchcote from UV - whew, DONE.

Steve I know this is not what a tech who charges by the hour can do but 
I defty water to infiltrate this type of wrap - I do not like doing 
pointless antenna maintennance and feel that an investment up front on 
high end materials like Scotchkote is well worth the drudgery of a 
failure that could have been avoided during initial assembly!

73,

Jim, K4OJ



K7LXC@aol.com wrote:

>In a message dated 10/10/02 11:53:09 AM Pacific Daylight Time, KI7WX@aol.com 
>writes:
>
>  
>
>>With the coax choke approach what are folks doing to terminate the coax 
>>    
>>
>into 
>  
>
>>pigtails for connection to the feedpoint? In my station I've always avoided 
>>coax terminations and junctions which don't end in a fitting that I can 
>>properly waterproof.
>>    
>>
>
>    I agree. Jim and Steve aside, I haven't seen ANY split coax 
>weatherproofing that was worth anything and my experience has been that it's 
>almost impossible to keep water from running down the shield (So THAT'S where 
>that puddle of water in the shack came from!). 
>
>    One way to do it is to use those little dipole center insulators with the 
>built-in SO239. The ends go to the feedpoint and the feedline plugs into the 
>UHF female socket. 
>
>Cheers,
>Steve     K7LXC
>TOWER TECH 
>_______________________________________________
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>  
>



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