Sat, 16 Mar 1996
Hello OMs!
Does an Andrews Female N-connector that has been PROPERLY installed on Andrews LDF5-50 7/8 inch Hardline need to be sealed against moisture entry?
Here is my situation. I have a run of Andrews LDf5-50 terminating at the top of my tower. It has a CORRECTLY installed Female N type connector with the connector pointing straight up. Mted to the female connector is an Andrews manufactured jumper with a Male N-Type connector on LDF4-50 1/2 inch hardline. The coonector on the jumper points straight down into the female connector. The jumper has, what appears to be a plastic collar down about 3 inches of the half inch. When I installed this stuff last September I did not wrap it with tape or coax seal. At the time it appeared that both ends would be waterproof due to the design of each connector,etc.
Well, yesterday a new sustained winds record was broken here in the Greenville, SC area. The winds were clocked at 87 miles per hour, shattering the old record of 72 MPH. I spent 15 minutes indoors looking up at my towers and watching my antennas being tossed about like rag dolls. Fortunately there doesn't appear to be any damage and fortunately the winds all came from the same direction and my antennas were pointing in to them. What worries me is the possibility of rain water being forced by the winds around the Hardline connector seals. Having been in a Typhoon on Guam and seeing water pouring out of the electrical outlets after being forced into the A/C entry conduit by high winds, I wonder if the same will happen to a PROPERLY installed connector. Are the Andrews connectors designed with such calamities in mind? Would sealing the whole splice keep any trapped moisture from exiting? Or should I just leave it the way it is? Any thoughts? Thanks in advance.
73 Ken
Sat, 16 Mar 1996
... as you know, the Andrew connectors are designed to be pretty weatherproof by using tight tolerances and O-ring gaskets in a couple of places. It is ALWAYS a good idea to weatherproof any connector joint; in fact, it is done practically 100% of the time by professional installers.
The Andrew recommended method is:
1) Apply two wraps of electrical tape over the joint (I recommend Scotch 33 or 88 myself).
2) Apply a layer of butyl rubber vapor wrap over the joint making sure that there are no air cavities or openings in the wrap. BTW, this is BETTER than CoaxSeal.
3) Apply 2 wraps of electrical tape over the joint with the final wrap going UP to minimize water migration.
4) Somewhat optional -- coat joint with Scotch-Kote sealer. I've seen some guys use spray urethane over the joint. It's another layer of protection whichever you use.
This technique should be used with ANY outdoor coax joint. It'll last for years and when you take your razor knife and open the joint up, it'll be just like new inside.
73 and good luck, Steve K7LXC
Sat, 16 Mar 1996
>Hi, Steve. I've been doing the tape-ScotchKote-tape thing, but not the >vapor wrap. What is this stuff and where should I look for it?
>Hiya, Steve --
Good question, actually. I didn't mean to be so hard on CoaxSeal (personally I don't care for it) but it will work in this kind of scenario. The problem is most guys apply it DIRECTLY to the connector which makes the connector unusable again. YUCK! Install the CoaxSeal OVER the first layer of tape and it will work.
As far as the butyl rubber vapor wrap, try the yellow pages for a local Andrew, DB Products or Antennas Specialists dealer; they should have it. The manufacturers always pack some in with some of there products but you may be able to get small quantities. Otherwise, check back with me a a few weeks --I may have some for you.
73 and good luck, Steve K7LXC
Sat, 16 Mar 1996
>What is this stuff, where is available and does it have a Scoth part #?
There are 2 tapes - Super 33+ and Super 88; 88 is about 20% thicker but they have the same properties. Any electrical supply store or electronic distributer that handles Scotch products will probably have them. They're $3-4 per roll but worth it. Do yourself a favor and don't use the "10 rolls for $1.99" hardware store specials.
>I know Scotch makes a "self-annealing" tape but I can't seem to find it anywhere in Northern new Jersey. Does anyone know the Scotch part # for this tape, too?
3M has a number of products in this line and I don't have the catalog. The phone number I have is an old one so I'll try to get you a number you can call to get additional product info.
>Let's see if I have this right: You apply a total of 5 layers of tape over the joint?
Well, four is usually sufficient but I was giving the Andrew spec. This is an bomb-proof, highly reliable industrial-standard weatherproofing technique. That's what you want in your tower and antenna system, don't you?
73 and good luck, Steve K7LXC
Sat, 16 Mar 1996
I have already researched this thread with 3M back in December. The product that you guys are looking for is Scotch 130C, Linerless Rubber Splicing Tape. It is a self sealing tape used in high voltage applications. Several of the PVRCers use this tape in lieu of Coax Seal.
3M will fax/send you the Product data sheet upon request: 1-800-364-3577 or 1-800-245-3573.
The Data sheet on the 130C shows that it is HV, moisture sealing, UV resistant, WX extremes functional, etc...
73! Bill, N3RR@CAIS.COM
Sat, 16 Mar 1996
Walt,K2WK asks:
>I know Scotch makes a "self-annealing" tape but I can't seem to >find it anywhere in Northern new Jersey. Does anyone know the >Scotch part # for this tape, too?
I use either Scotch #23 Rubber Splicing tape (it is described on the package as High-voltage, Self-fusing, Insulating Tape based on Ethylene Propylene Polmers), or Scotch 130C Linerless Rubber Splicing Tape (again described as based on Ethylene Propylene Polymers). I'm told both of these don't stand up well to UV so they should be covered with two layers of Scotch #88. I normally don't cover the Scotch #88 with anything and I have had no problems. But I have also used Plasti Dip Spray-On over the #88 for connections that will be on or under the ground.
73's Pete-N8ATR n8atr@en.com
Sat, 16 Mar 1996
I have always been able to find the Scotch 130C and super 88, and bulk UV okay wire ties at Grainger. They have locations all over the place. If you work for someone that has an account with them, then you probably can buy at the wholesale price (I do).
73 de N1PBT...ron (rrossi@btv.ibm.com)
Sat, 16 Mar 1996
3M has a home page that can help you identify and locate their products. Have a look at http://www.mmm.com if you have a graphical web browser. I tried to look up Scotch-Kote, but my text based browser doesn't work with 3M's search page. I can look it up from work on Monday if noone beats me to it.
73,
Greg AA0XZ gnunn01@mail.coin.missouri.edu
Disclaimer: I work for 3M but don't have anything to do with tape.
Sat, 16 Mar 1996
Just a couple of additional thoughts on Steve's comments about sealing connectors.
>1) Apply two wraps of electrical tape over the joint (I recommend Scotch 33 or 88 myself).
Scotch 88 is really the all weather tape to use. Scotch 33 tends to get brittle in cold weather and has more of a tendency to lose its grip with time, weather, and just a little stretching. 88 is a little more expensive but I would never use anyhting else outdoors.
>2) Apply a layer of butyl rubber vapor wrap over the joint making sure that there are no air cavities or openings in the wrap. BTW, this is BETTER than CoaxSeal.
Butyl rubber tape is available from most good electrical supply houses.
>4) Somewhat optional -- coat joint with Scotch-Kote sealer. I've seen some guys use spray urethane over the joint. It's another layer of protection whichever you use.
I think Scotch-Kote is a waste of time if the connection is exposed to the sunlight. Within a year it has degraded from the ultra-violet and has pretty much flaked off (at least in Colorado). It is fine for direct burial, for which it is intended. I actually like Plasti-Dip, which is available from most hardware stores and is used to dip tool handles for insulating them. Use the black color for better UV resistence. It can be painted on (pretty thick goop) or there is a spray version as well.
For things like splitting out the pigtail lead of coax to hook to a sloper or a dipole (after the balun) I do a couple of layers of Scotch 88 with alternating layers of the Plasti-Dip by just dunking the end into a gallon can of the stuff. Put some masking tape over the terminal lugs to eliminate having to clean them off.
Another technique I use for weather proofing the pigtail ends of coax is to put some heat shrink over the entire length of exposed dielectric up to the point where the braid splits off. Then, taking a length of larger diameter heat shrink, I cut a little slot in the middle and place that over the jacket and heat-shrink-covered dielectric in such a way that the braid sticks out the little slot. I dip this whole thing into a thinned down version of Plasti-Dip (you don't need their thinner--it is just expensive paint thinner/mineral spirits). This thinned down material soaks into the braid--filling up the gaps to reduce the possibility of wicking moisture into the region between the braid and center conductor.
Yep, I know it is a lot of work, but how many times do you want to replace your coax because it got water inside and the losses sky-rocketed.
73 John W0UN email broz@csn.net
Sat, 16 Mar 1996
Thanks for all the responses guys! The answer is Yes. Extra waterproofing is needed for an absolute watertight seal. Every splice at my QTH is triple sealed with layers of electrical tape and Rubber sealing tape.(coax seal). This is the way I have always done it. This combo has always worked well for me. The N, PL-259, whatever, type connectors remain shiny and uncorroded when they are taken apart when sealed in this manner, even after years of use. There was a reason I chose to leave this particular joint unsealed except for the Andrew connector seals.
I don't remember why though. HI!
I climbed the tower earlier today and took the connector apart from the 7/8 and am happy to say that it was bone dry with no corrosion internally as far as I could inspect. I reassembled and sealed it using the proper techniques. I can say though that properly installed, genuine Andrew connectors do a good job of keeping the moisture out. I was certain that water would have made its way inside after those 87 MPH winds with rain that we had yesterday. Extra preventive measures never hurt. Thanks to all who responded with their personal experiences.
73 Ken KP4XS/W4