[NLRS] [BC'ers] Coax to antenna feedpoints: an unbroken run or a rotor loop transition connection?

[Dr. Gerald N. Johnson]

Yup. Going to an extreme electricians used to repair underground 
services with 5 layers of tape and scotchkote. And I've dug that up from 
9 feet underground and it was clean inside when I cut the tape off.

The Story County ARC repeater on a water tower used Belden 9913 coax for 
20 or 30 years, a coax notorious for getting water inside. The repeater 
manager is an electrician and he applied the 5 layers of tape and 
scotchkote to the connections and that coax never showed the repeater 
desensing typical of water in the coax or connectors. It has a run of 
7/8" Heliax now after the owner of the water tower took down the 9913 
and antenna to paint the water tower. It does work somewhat better with 
the Heliax.

73, Jerry, K0CQ

On 8/27/2015 10:12 PM, Joe wrote:
> What I have always done since 1975 to waterproof like these types of
> connections is this,
>
> The spiraly would very tight scotch 33, then sprayed a good outdoor UV
> stable spray paint. full;y wetting it.
>
> then when tacky another layer of 33, then another spraying then another
> layer of 33 and final spraying.
>
> even after 20 years when cut open with a knife the silver connectors
> look brand new still.
>
> Joe WB9SBD
> Sig
> The Original Rolling Ball Clock
> Idle Tyme
> Idle-Tyme.com
> http://www.idle-tyme.com
> On 8/27/2015 9:12 PM, Dr. Gerald N. Johnson wrote:
>> The ARRL's book on Towers has a chapter on weather proofing
>> connectors. Scotch 33 is central, 88 is good too. Multiple layers
>> alternating either tape and Schotchkote liquid is good when the liquid
>> can be found. Its getting uncommon. Liquid tape can be had a lot
>> easier and should be good too. Stretch the tape a lot to take care of
>> different diameters, but cut the end and don't stretch the last couple
>> turns. Don't break the tape from the roll by stretching it, it will
>> peel back in time. Imitations of the real Scotch tape product
>> generally don't work nearly as well.
>>
>> Antenna feed connectors need waterproofing on both sides, the coax and
>> the antenna feed details. Ordinary chassis mount connectors generally
>> used for that are NOT water tight and let water get into the coax. Hot
>> melt glue or liquid tape should work there. Also sprayed layers of
>> clear Krylon or Rustoleum should be good too. A C3I 432 yagi kit I
>> assembled last month recommended the clear Krylon.
>>
>> 73. Jerry, K0CQ
>>
>> On 8/27/2015 8:43 PM, Scott Neader KA9FOX wrote:
>>> I'm far from an expert, but I did have one install my stuff (Rev. Paul
>>> W0AIH). He ran coax to the top of the tower, then put a connector and
>>> barrel at the top, then transitioned to a piece of coax referred to
>>> as the
>>> "rotor loop"
>>>
>>> Keep in mind that many of my cables (and hopefully yours) are of low
>>> loss,
>>> hardline type. You can't possibly run hardline as your rotor loop, so
>>> you
>>> will need to transition anyway. Having ALL of them transitioned this way
>>> does allow for easier servicing, as you suggested.
>>>
>>> Also, even if you aren't using hardline, you still need special
>>> "flexible"
>>> cable for your rotor loop. You don't want or need that for the whole
>>> run,
>>> just the rotor loop at the top. There are some good low-loss cable for
>>> this purpose, from LMR and others.
>>>
>>> Lastly, while this may not be ideal, I have no such "junction box" at
>>> the
>>> top and I've never seen anyone do that. Just use a barrel connector or
>>> whatever you need to join the pieces of coax... use lots of
>>> waterproofing
>>> (elephant snot, rubber sheets or whatever your preference is) and
>>> then tape
>>> that up good with Scotch 33, etc. Your junction box will probably just
>>> fill with water anyway. :-)
>>>
>>> - Scott KA9FOX
>>>
>>> On Thu, Aug 27, 2015 at 11:19 AM, David Palm<thepalmhq at gmail.com> wrote:
>>>
>>>> I have new antennas to put up for 50/144/222/432. I may have time to
>>>> get
>>>> them up before the September contest.
>>>>
>>>> My question is whether most of you run an unbroken cable all the way
>>>> from
>>>> your lightning arrestors to the feedpoint of the antennas (with enough
>>>> extra at the top to create a rotor loop), or whether you do a run
>>>> from the
>>>> arrestors to a junction box at the top of the tower, then transition to
>>>> shorter rotor loop sections to the feedpoints? It's an additional
>>>> hassle
>>>> and some loss involved in the second scenario, but now I'm thinking
>>>> that in
>>>> terms of being able to service individual antennas it would be nice
>>>> to be
>>>> able to disconnect them at the top of the tower and have only a
>>>> relatively
>>>> few feet of cable to wrangle with.
>>>>
>>>> Your thoughts would be helpful, as this will all be happening quite
>>>> soon.
>>>>
>>>> 73,
>>>>
>>>> David W9HQ
>>>>