[TowerTalk] PL259 Connectors

[Bob K6UJ]

Howie,

Thanks for sharing.  Its great to know how the pros do it !

Bob
K6UJ





On 5/15/16 12:44 PM, Chuck Dietz wrote:
> Great post, Howie.  Lots of good info there.
>
> Chuck W5PR
>
> On Sun, May 15, 2016 at 12:39 PM, Howard Hoyt <hhoyt at mebtel.net> wrote:
>
>> On 5/15/2016 12:00 PM, towertalk-request at contesting.com wrote:
>>
>> From: <john at kk9a.com>
>>> ...I'm not sure why more hams don't do what the pros do.
>>>
>> I've been watching the discussion with some interest to see where it would
>> go, and to see if anyone has come up with a better system than the 3/4"
>> tape over the connectors/butyl seal/2" tape overall system.  I've been a
>> broadcast engineer for over 30 years and have used the 2" wide Andrew tape
>> and butyl weatherproofing exclusively. It is also important to tighten with
>> wrenches or pliers to inhibit loosening from vibration or wind movement.
>> To date I have not had a connection fail due to water intrusion using this
>> system.  If you examine the tens of thousands of connections on broadcast
>> towers across the world on Heliax and coax products, this is what broadcast
>> engineers and tower riggers use.  Keep in mind this sealing system has to
>> be in use 24/7 and at thousands of feet up in the weather and last for
>> years.   The very worst I encounter when dis-assembling a connection
>> protected in this manner is tape adhesive residue on the connectors, but
>> never moisture or corrosion.
>>
>> The 2" wide thick tape is an important part of the system; when used as
>> the top seal it inhibits the butyl from extruding between the wraps of
>> tape, which can be a problem with 3/4" wide tape.  It also allows a more
>> generous overlap for better adhesion.  The high-quality tape Andrews specs
>> (not always 3M...) will not lose adhesion even after years of UV and high
>> winds.  Of course the last few wraps must be made at low tension and laid
>> flat without wrinkles, AND making sure the surface of the tape it is
>> adhering to has no dust, oils or greases to inhibit adhesion. (see below on
>> using greases)
>>
>> Packing the connectors with any sort of grease is problematic for a few
>> reasons: Some greases have a fairly high film strength, and the wiping
>> action of the mating parts may not fully displace it resulting in a poor
>> connection, compatibility with dielectrics or seals (BNC/N) is not
>> guaranteed, and unless the product is guaranteed to be free radical and
>> moisture free (most are not), you are potentially adding a source of
>> corrosion.  Also, it can bleed, it makes a mess and seems to get on your
>> hands/gloves no matter what you do so you end up getting it on the
>> connector and coax.  This film can then interfere with the adhesion of the
>> primary seal you put on the outside of the connectors.  An example of this
>> problem: when installing flanged hardline or Heliax connectors you must
>> grease the o-rings, but then you must be be meticulous about cleaning your
>> hands/new gloves before you install any grounding kits which include
>> taping.  Basically, if you do the external sealing correctly you just plain
>> do not need grease with non-flanged Heliax or coax connectors.
>>
>> You must be very careful how you use dual-wall adhesive heatshrink for use
>> on flexible cables, even the thick marine grade type.  It is important to
>> clean the jacket with a degreaser such as isopropanol before installing to
>> ensure a good bond.  Also, extend the heatshrink 4-6" onto the coax to
>> ensure the zone near the connector remains relatively rigid even if the
>> bond at the end fails.  I have had factory-supplied FM antenna multi-bay
>> phasing harnesses weatherproofed with short lengths of adhesive heatshrink
>> tubing fail after being aggressively flexed by wind in cold weather when
>> the hot-melt glue became very stiff and brittle.  The bond between the glue
>> and coax jacket then failed and resulted in moisture intrusion.  I have
>> since installed cables with much longer heatshrink and many coax supports
>> to inhibit any movement.  I took a picture of this exact connection after
>> rework on my website here (note broken phasing network cover due to falling
>> ice):
>>
>> https://proaudioeng.com/wp-content/uploads/2016/05/20140822_103713.jpg
>>
>> For connections with hardware such as lugs under screws and nuts, as well
>> as sealing exterior cabinet panels we use Scotchseal 800 which in my
>> experience will give years of life and seals pretty well to metals and
>> plastics even when exposed to UV and weather.
>>
>> Remember: bonding occurs at the molecular level which means the molecules
>> you wish to bond together must be able to interact.  Oils, moisture, and
>> dust can all inhibit tape/adhesive bonding. Cleanliness is imperative.
>>
>> Just my $0.02 worth,
>>
>> Howie - WA4PSC
>> CE - WXYC-FM
>> UNC Chapel Hill, NC
>>
>>
>>
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