How To Weatherproof Outside Coax Join

March 11, 2022

If you need to join a coax cable outdoors, special care and attention needs to be made to ensure that water cannot penetrate inside the cable. If it does, you could get problems with your aerial or satellite TV reception. Waterlogged coaxial cables are actually very common and heavily waterlogged cables can damage the TV equipment that they are connected to. In this article I discuss the ways that you can weatherproof/ waterproof TV cables outside. Let’s begin.


Can You Join A Coax Cable?

Before we discuss the ways and means of how to join a coax cable, one of the most common things I get asked is can you actually do this? And the answer is yes, it’s an old wives tale that TV cables can’t be spliced. You just have to make sure that this is done correct. You need to make sure you have the correct sized coax connectors for the cable you wish to join and you fit them properly. There are signal losses associated with coax joins but they are negligible. If you have multiple joins on a single cable you may want to consider replacing it but otherwise you will be fine.


If you are going to join coax cables I recommend using F connectors for this as they are superior to standard coax IEC plugs. You will require two F plugs and one F coupler, often called a barrel connector. Please check out our video on how to do an F join.


Weatherproof F Connectors

You can purchase F plugs that are designed for exterior use. These are usually compression type plugs which require a specialist tool to fit the plug to the cable. There are multiple brands on the market but I use the Cablecon compression plugs for this task. When installed correctly the join(supposedly) can be completely submerged in water and it will still be okay. I wouldn’t put this to the test mind and I would still try to wrap in self-amalgaming tape so offer further weatherproofing but this isn’t always possible are connections are LNB’s where the pull down cap prevents you from doing this. The connector has internal O rings that are effective when the plug is fully tightened when you install, so you will need to tighten with a spanner(11mm) for this to be effective. This is usually only a quarter turn after you have finger tightened.


Self Amalgamating Tape

Self-amalgamating tape is what I would always use for outdoor TV aerial/ Sat/ Sky TV joins. When you have connected the two pieces of coax cables together it wraps around the join to weatherproof. It usually has aplastic strip on one side which needs to be removed and this needs to be the side that wraps around the join itself, so it’s on the inside not the outside. When wrapping the cable is flexible and easily extendable, you need to pull it to about twice it’s natural length when wrapping around the cable. Personally, I always do two wraps, covering about an inch of the cable either end just to make sure.


Silicone Grease

One thing you could use for exterior coax joins is silicone grease. It’s not ideal for exposed joins where you should use self-amalgamating tape or an exterior junction box, but it is perfect for weatherproofing connectors at satellite LNB’s or inside TV aerial splitter boxes/ masthead amplifiers or other types of masthead equipment. I would usually use this as LNB connections because even though LNB’s have a pull-down rainwater cover, this doesn’t always offer the most reliable protection and often the pull down cover doesn’t even fully cover all of the F plug itself. I would use a smear of silicone grease in this instance to be sure, I would even use it on weatherproof connectors and it helps preserve the exterior of the weatherproof plugs meaning that if you ever need to unscrew at a later date, it will easily undo. Silicone grease is particularly helpful when doing TV aerial or satellite dish installations in seaside properties or marine environments when the water has a tendency of driving itself in all places.


External Junction Box

The cable join can also be weatherproofed by placing this inside an externally mounted junction box. There are many types of purpose made external junction boxes on the market, including masthead models that can be cable tied directly onto aerial masts. Many of these will have purpose made cable entry/ exit slots for the cable to enter and exit nicely.


Alternatively you could get a small IP56 or IP66 junction box typically used by electricians and electrical contractors and place your cable join in here. You may still want to wrap the join in self amalgamating tape or give a smear or silicone grease. It’s a good idea to use cable entry grommets where the cables enter the junction box and to keep these on the bottom side of the box when install so that any rainwater drips away rather than inside.


Join Cable In Protected Position

If you have a bit of flexibility as to where you are joining your coaxial cable, you may want to put this in a protected position to help protect for weathering. You could tuck this up underneath a soffit or behind something. I have personally in the past joined cables entering lofts outside and poked the join so that it’s inside and placed cable joins underneath rooftiles. Each installation is different so you will have to see what’s available to you.


Make Sure You Install Equipment The Right Way Up

I touched on this above and it may seem obvious, but I see lots of waterlogged cables and aerials simply because it was installed the incorrect way up. Most TV aerial equipment will have small holes on it to allow water/ moisture that has entered to escape again. On TV aerials this is usually on the dipole, this is the part that the coax is terminated into. I have lost count the amount of TV aerials installed the incorrect way.


Ensure You Have A Drip Loop

Try to ensure that you have a drip loop on your cabling where it enters the termination. This isn’t necessary with equipment that has a connections directly on the underside but where the cable enters into equipment, like cable junction boxes, aerial dipoles etc, the cable as it enters or exits should immediately be directed down so that any rainwater than goes onto the cable drips away instead of in. This is also true where cables enter through walls into houses.


External Cable Join Questions – In Blog Comments Section Only Please

We only respond to comments/ questions arising from our blogs that are posted within the Blog Comments Section at the bottom of each blog. This is because we are a small business serving Sussex/ Kent only in South East UK and our phonelines are intended for CUSTOMERS ONLY who require installations, estimates and quotes.


Please do not call our telephone lines

Please do not fill in our website contact forms or e-mail your questions privately.


We do not have the time, staff, motivation, energy or desire to provide over the phone free technical support and advice, so please keep your comments within the Blog Comments Section only please. That being said, I will help where I can.


Until next time,


Latest Blogs

March 31, 2023

What Is Signal Polarisation?

Signal polarisations used with TV aerials, satellite, & wireless telecoms. Inc info on different polarity types & how to align correct.

March 15, 2023

UHF/ RF Modulators For TV Systems Explained

Read this for info on UHF/ RF Modulators for TV Systems. Inc Tips, advice, & instructions on how to install a modulator. Create TV channel.

March 9, 2023

Broadband/ Internet Without A Telephone or Landline

Read this for info on how to receive broadband/ internet without a telephone or landline at your property. Inc help, advice, pro's & con's.