If you need to bring a TV signal from an antenna into your house; set up a
computer network in your home; or hook up cable TV, an FM radio or a cable
modem chances are you'll be working with coaxial cable. Coaxial cable, often
simply called "coax," is that fat black cable that cable TV
companies install. So you probably already have coax in your house.
What with multiple televisions, a computer or two and Lord knows what else
is coming down the pike, you're apt to find a lot more coax in your life.
Here's a primer that will take the mystery out of working with coax and show
you how to make a couple of essential coax connections.
About Coax
Coax consists of a center wire surrounded by insulation, which is in turn
surrounded by an outer conductor of braided wire that serves as a grounded
shield, enclosed in an outer jacket of insulation. The shield minimizes
electrical and radio frequency interference. (Sometimes there's a layer of
foil between the interior insulation and the outer conductor as well.)
Coax gets its name because its two channels run concentrically
along the same axis. It's quite an old product, originally designed to
carry analog telephone signals at high capacity with little electronic noise.
It's also a preferred product, virtually weatherproof and much more durable
than "twinlead," the old-fashioned flat
wire originally used for TV. Signal performance is also superior. Coax
doesn't pick up unwanted signals, and it's not affected by contact with metal
structures. And although cable installers often use special standoff supports
when attaching coax to exteriors, all you need to route coax inside your
house are coaxial cable straps.
Coaxial cable is also easy to work with. It's pretty simple to tap into an
existing coaxial line to hook up a second TV or extend a computer network
("splitting" the line, as it's called). All you need are a few
tools, an additional cable and a splitter, a small device that divides the
cable's input signal to provide an equal signal at each output. Ordinary
tools are fine for making a couple of connections, but if you're making a lot
of them, invest in a few inexpensive specialized tools: the work will be
faster and more professional. If you're hooking up more than one additional
unit, buy a splitter with three or four outputs, or terminals, instead of
two. This usually yields better results than splitting the line at each
device, which may weaken the signal.
Splitting and Extending a Line
This illustration shows how you split a single coaxial cable line and send a
new branch to a new location. First, let's assume you only have one TV (the
"original device" in the illustration) connected to a coax line.
Unscrew that screw-on connector from the back of the TV. Mount the splitter
to a baseboard or similar location with the mounting screws provided, or use
1 1/4-inch drywall screws. Be sure to mount the splitter within reach of
the original coax line. Screw the original connector into the tap marked
"input" on the splitter.
Next, you'll need two new coaxial cables, one for the original device and
one for the new device. You can either buy them with connectors already
attached or put them together yourself the next page shows you how. Screw one
end of each new cable to an output tap on the splitter and the other end into
the input jack on the back of the TV or other device.
Support the cable between the splitter and the devices with coaxial cable
straps nailed to baseboards every 2 or 3 feet. If you need to run cable
through interior walls, drill passage holes in corners or other inconspicuous
locations using a spade bit. You can run cable through exterior walls almost
the same way. To keep water out of your walls, always make a drip loop where
the cable enters your home, as shown above. Be sure to seal the exterior hole
with silicone caulk.
Attaching a Coaxial Cable Connector
Coaxial cable connects to electrical equipment with F-plugs, which clamp onto
the stripped cable and screw or slide onto the device or splitter. (If you're
adding a new cable, it'll need F-plugs on both ends.)
To put an F-plug onto a length of coax, cut the cable's end square with
lineman's pliers. Next comes a two-step stripping
process. First, use a coaxial cable stripper or a utility knife carefully to
remove 1/2 inch of the cable's outer covering. As shown in the animation,
peel back the woven outer conductor (and foil, if any), folding it back over
the outer insulation. Second, strip 1/4 inch of the inner insulation to
expose the slender center conductor. To attach the connector, first slip its
ferrule onto the cable. Then push the body of the connector over the white
insulation, fitting the sleeve under the outer conductor and foil. The white
insulation will bottom out in the connector, and the inner conductor will
protrude through the hole in the end of the plug. Finally, crimp the ferrule
with a coaxial cable crimper or pliers to hold the connector in place.
Tip From the Pros
The woven outer conductor lies in an irregular cavity just underneath the cover, and it's virtually impossible to cut all the way
through the outer jacket without damaging the conductor beneath. Adjust the
blade of your cable stripper or manipulate your utility knife to cut just
partway through the jacket. Bend
the jacket at the cut, and you can pull it free without damaging the outer
conductor.
