...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
>_______________________________________________
>AN Wireless Self Supporting Towers at discounted prices,
>See http://www.mscomputer.com
>
>Wireless Weather Stations now $349.95. Call Toll Free,
>888-333-9041 for additional information.
>_______________________________________________
>Towertalk mailing list
>Towertalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
--- StripMime Report -- processed MIME parts ---
multipart/alternative
text/plain (text body -- kept)
text/html
---
|