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Author Topic: Shipboard connector weatherproofing- US Navy style  (Read 2290 times)
VIPER21700
Member

Posts: 22




Ignore
« on: August 19, 2012, 08:39:41 AM »

Ok gents,
 I dont know if anyone needs this information, but this is how we weatherproof antenna connectors on board ship. Ive pulled antennas down that have been weatherproofed this way 2 years later and the connectors have zero corrosion on them.
Required Materials
1 roll standard black 1" wide electrical tape (3m works bests, heat doesnt seem to affect it as much)
1 roll 1.5" wide self vulcanizing rubber tape (doesnt stick to anything but itself)
tube of dielectic grease, most auto parts stores and radio shack carry this, do yourself a favor, keep a tube in your toolbox.
1 bottle of scotchkote electrical insulating varnish
This method is called the three two three method, and is taught by MARMAC at the Antenna Maintanance School
Step 1-
 place a thin coating of grease around the threaded part of the antenna connection, and install your feed line

2- starting by the antenna (for this purpose, we will use the base of the antenna's connection as top, and the bottom of the feedline connection as bottom) apply a tight overlapping continuous wrapping of electrical tap until it is approx 2" below the bottom of the feed line connector. Ensure there are no wrinkles or open spaces in the wrapping.
3- Wrap again, this time from the bottom back to the top, then work your way back down to the bottom.
4- Using your Rubber self vulcanizing tape, repeat the same process, once down, and once back up (This is the 2 portion of the method)
5- SHAKE YOUR CAN OF SKOTCHKOTE!!!! This is important, the varnish likes to settle.
6- Apply a thin coating of skotchkote to the entire area, ensure any gaps in the tape get an extra heavy coating.
Wait thirty minutes between coatings, and apply two more coats.

As I said, not sure if anyone needed this, just paying some information I learned from work forward. This method work. We had antennas mounted right above our exhaust stack on my last ship, and they were in the worst enviroment you could imagine, salt water spray, high temperatures, corrosive exhaust vapors, and constant UV. We removed them over a year later, and the connections were as clean as the day I originally installed the antennas.
Hope this helps someone!
73
KK4LAK
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VIPER21700
Member

Posts: 22




Ignore
« Reply #1 on: August 19, 2012, 09:57:45 AM »

Oh and one other thing, the biggest VSWR creating issues we had on ship were all due to bad weatherproofing! Every antenna on our ship was removed at least once every year or so for repairs/refurb, and they were cleaned and inspected at least once every six months. If you follow these guidlines, you should be ok (as long as your antenna is built correctly)
ALSO MAKE SURE YOU INSTALL YOUR ANTENNAS WITH NON-FERROUS HARDWARE!!! You dont even want to know how much of a pain it was to track down a high VSWR issues that was due to a handful of rusty bolts hidden underneath silicone sealant....
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N4NOO
Member

Posts: 106




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« Reply #2 on: August 20, 2012, 07:52:19 PM »

Very good to know!  Thanks for the info!

Rick - N4NOO
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K7KBN
Member

Posts: 2788




Ignore
« Reply #3 on: August 20, 2012, 09:03:33 PM »

Oh and one other thing, the biggest VSWR creating issues we had on ship were all due to bad weatherproofing! Every antenna on our ship was removed at least once every year or so for repairs/refurb, and they were cleaned and inspected at least once every six months. If you follow these guidlines, you should be ok (as long as your antenna is built correctly)
ALSO MAKE SURE YOU INSTALL YOUR ANTENNAS WITH NON-FERROUS HARDWARE!!! You dont even want to know how much of a pain it was to track down a high VSWR issues that was due to a handful of rusty bolts hidden underneath silicone sealant....

In a high-density RF environment, SWR changes might be the least of your worries!  Google "rusty bolt effect"...
Logged

73
Pat K7KBN
CWO4 USNR Ret.
AA4HA
Member

Posts: 1397




Ignore
« Reply #4 on: August 22, 2012, 09:01:38 AM »

Ok gents,
 I dont know if anyone needs this information, but this is how we weatherproof antenna connectors on board ship. Ive pulled antennas down that have been weatherproofed this way 2 years later and the connectors have zero corrosion on them.
Required Materials
1 roll standard black 1" wide electrical tape (3m works bests, heat doesnt seem to affect it as much)
1 roll 1.5" wide self vulcanizing rubber tape (doesnt stick to anything but itself)
tube of dielectic grease, most auto parts stores and radio shack carry this, do yourself a favor, keep a tube in your toolbox.
1 bottle of scotchkote electrical insulating varnish
This method is called the three two three method, and is taught by MARMAC at the Antenna Maintanance School
Step 1-
 place a thin coating of grease around the threaded part of the antenna connection, and install your feed line

2- starting by the antenna (for this purpose, we will use the base of the antenna's connection as top, and the bottom of the feedline connection as bottom) apply a tight overlapping continuous wrapping of electrical tap until it is approx 2" below the bottom of the feed line connector. Ensure there are no wrinkles or open spaces in the wrapping.
3- Wrap again, this time from the bottom back to the top, then work your way back down to the bottom.
4- Using your Rubber self vulcanizing tape, repeat the same process, once down, and once back up (This is the 2 portion of the method)
5- SHAKE YOUR CAN OF SKOTCHKOTE!!!! This is important, the varnish likes to settle.
6- Apply a thin coating of skotchkote to the entire area, ensure any gaps in the tape get an extra heavy coating.
Wait thirty minutes between coatings, and apply two more coats.

As I said, not sure if anyone needed this, just paying some information I learned from work forward. This method work. We had antennas mounted right above our exhaust stack on my last ship, and they were in the worst enviroment you could imagine, salt water spray, high temperatures, corrosive exhaust vapors, and constant UV. We removed them over a year later, and the connections were as clean as the day I originally installed the antennas.
Hope this helps someone!
73
KK4LAK

This is a great video on how to do a real professional job on connector weatherproofing;
http://www.youtube.com/watch?v=nhSSfOQGdIM

Just mentally modify this for a connection to an antenna connector. I personally think he used too much mastic and usually for a kit I can do 4-5 connectors with the same technique.

A great starter tape is Scotch super 33+ tape. Do not use the ten cents a spool tape. Most of it is junk and practially has no adhesive properties.

Here are some part numbers for the Silicone Grease;
*     3M Products - 3M Silicone Paste       Mfg Part #: 051135-08946
*     Dow Corning #4 - Electrical Insulating Compound    This comes in a dark green large toothpaste like tube. I swear by this stuff. I squirt it inside of every electrical connection I have that might come in contact with water or corrosive environments It is food grade and is great for O rings or rotary switch contacts too (like a chlorine atmosphere in a water treatment plant or around ozone gas).

BTW, do not get this stuff all over the place, tape will not stick to silicone grease. You want to flood the inside of the connector body (inside of the PL-258 shell and where the PL-259 plugs into the SO-239 female connector). This also gives water no place to be. It also keeps the connector contacts from being exposed to oxygen where they may corrode.

I learned a very similar technique to the Navy way that is used for high voltage connections in an explosive gas environment like a refinery;

The first layer of tape is important..if you ever plan on taking that connection apart you want that double wrap of something like Scotch #33 from as close to the chassis as you can get, slightly stretched tape wraps with 50% overlap between each turn, all the way down to the coax and at least two conductor diameters past the end of the connector body. You want this to look "pretty", back down and back up.

The rubber, self vulcanizing tape is also known as N-Butyl tape. It is in rolls that are in waxed paper layers so it does not turn into a big gob of rubber. Do not have any silicone grease, dirt or oils on your hands when you put this stuff down. You want to stretch it as you make the wrap from as close to the chassis and down over the layer of #33 tape. In cold or wet environments it may be quite stiff to handle. Once you put it down it will be about a 1/4" inch thick and you use your hands to knead it like dough, squishing it into every nook and cranny on the connector on the tape until it is a neat looking blob of black mastic.

I am not endorsing this seller. There are lots of places who sell this stuff. Here is one example of a "kit" that is sold for this type of connector;
http://www.tessco.com/products/displayProductInfo.do?sku=18264

After the N-Butyl self amalgamating tape is put down, neatly blobbed and has no gaps then you can use Scotchkote. The Scotchkote acts like a solvent for the N-Butyl and makes that N-Butyl tape really soft and sticky. It is also messy but works great.

I finish up with Scotch® Super Vinyl Electrical Tape 88. It is thicker than the 33 tape and available in a wider spool of like 1-2" You again want that slight stretch and a very pretty and non-bubbly layer that goes much further down the feedline than the original type 33 layer or the N-Butyl. You can terminate this stuff into a slight bit of slop from the Scotchkote. It keeps the end from unraveling.

What is neat about this approach is that you can be pretty much 100% guaranteed that any problems you have in the future will not be due to water getting into the coax and if there is a connection failure it is because some twit was using the coax as a swingset and has torn the braid free from a crimp or solder connection in a PL-239 connector body (use crimp connectors if you can).

Oh, on long coax runs you will want to use something called a "Kellum Grip". It is like a stainless steel Chinese finger puzzle for cables to take the strain and loading. We use them at the top (and sometimes in the middle) of long vertical feedline runs inside of cell-site type monopole setups where the coax may end up weighing 600 pounds. Here is an example;
http://www.controlbooth.com/wiki/Kellems+Grip
I also use Kellum grips if I need to run coax vertically from a building to the tower but I also use something called a "carrier wire" to keep the coax from having any droop in it.
One of the failure modes on coax cable is an unsupported vertical run that gradually pulls the coax out of the connector body. On a tall tower you may have a Kellum grip (and a ground kit) every 75' up the tower. (ground kits at the top, bottom and with no center span with more than 75' unbonded. This prevents lightning flashover from blowing holes in your coax cable).

With the first layer of #33 tape as an underwrap you can always go back later with a sharp box cutter knife and cut the entire weatherproofing blob off and it is like shucking the shell off of a nut from a wallnut tree. Then from height, see if you can bomb your old beat up car with the tape blob <joke>
« Last Edit: August 22, 2012, 09:23:19 AM by AA4HA » Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
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