Don't buy cheap cable

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Quad-shield cable

High-quality cable has two layers of metal foil and two layers of braided wire to block interference.

Shielding is what counts when it comes to cable quality. It blocks interference and keeps the signal clean. Skip the economy cable and go right for the “quad-shield” product. Quad-shield costs twice as much as cable labeled “dual” or “double-shield.” But after spending big bucks on your TV or computer, skimping on coax just doesn't make sense.

Don't kink the cable

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Wrong

Avoid sharp twists or bends when working with coaxial cable.

The wire at the center of coax cable is molded inside a foam jacket to keep it away from the shielding and to block interference. If you kink the cable or bend it around a sharp corner, you crush the foam. At that point, the damage is done and there's no way to undo it. Never bend cable around a radius smaller than 3 in.

Don't pull too hard

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Wrong

Muscling wire through studs or joists will degrade picture quality.

Kinking and crushing aren't the only ways to damage the foam jacket surrounding the center wire. Pulling coax cable too hard tightens the braided wire shielding and compresses the foam (the way Chinese handcuffs tighten around your finger). That harms signal quality. The maximum pulling force for RG-6 cable is 35 lbs.

Don't run coax too close to electrical wiring

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Keep coax and electrical wire separate

Keep coax and electrical cables at least 6 in. apart. If the coax must cross over an electrical line, create a 90-degree intersection.

Electrical lines can cause nasty interference in coaxial cable. So keep coax cables as least 6 in. away from electrical cable, even if the cables are separated by wood or other building materials. To reduce any chance of trouble from phone lines, install “twisted pair” or shielded phone wiring.

Don't crush the cable

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No pinching

For kinder, gentler (and faster) cable stapling, use a stapler designed for the job. If you drive staples with a hammer, don't pound too hard.

There are a few kinds of staples made for coax, and all of them work wel—as long as you don't drive them in too far. Forced too tightly over the cable, they'll crush the foam jacket inside, causing the same trouble as a kink. If you're running lots of coax, buy a special cable stapler, which won't crush the cable. They're available at some home centers or online (search for “cable stapler”).

When using a hammer, don't pound too hard. The staple shouldn't bite into the cable; a loose hold is better than a tight hold.

Don't space staples evenly

When it comes to attaching coaxial cable, neatness is bad. And here's why: Any type of fastener squashes the cable slightly. When coax cable is deformed, it reflects portions of the signal toward the source. If the deformed portions are evenly spaced, the reflections become rhythmic, causing double imaging. On Internet and satellite cable applications, these reflections can disrupt service. Uneven spacing between fasteners eliminates rhythmic reflections. So how far apart should you place staples? As far as possible. Use only as many staples as needed to hold the cable in place. Running up the side of a stud, for example, you typically need just three: one top, one bottom, one in between. Just make sure that the “between” staple isn't exactly halfway between the other two.

Don't let the shield show

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Neatness counts

A single strand of shielding exposed at the connector can degrade the signal. A sloppy connection like this one ruins the signal completely.

The best cable-routing job can get fouled up if you aren't careful when you attach the end connector. Always fold back the foil and braided shield carefully before you attach the connector. A single strand of braid protruding into the connector area can ruin the signal. Double-check your work before you crimp or compress the connector.

Don't nick the center wire

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Cut cleanly

Use a coax cable stripper, not an electrical cable stripper.

The signal carried by the center wire actually travels along the outside of the wire, not through the inside. So a tiny nick in the wire can cause a big obstacle for the signal. That's why a special coax stripper (sold at home centers) is the only tool you should use to prepare the ends of the cable for connectors. Never use standard wire strippers or a knife.

Don't use screw-on connectors

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Crimping works better

Compression-type connectors grip cable firmly, without crushing the inner foam jacket as crimp-style connectors sometimes do.

Solid connections at the ends of coax cable provide a clear path for the signal to follow. Loose connections weaken the signal. End connectors that screw on over the outer jacket of cable can loosen up over time and even fall off. Instead, use crimp-ring style connectors and a special crimping tool (sold at home centers), or better yet, compression-style connectors.

Don't just finger-tighten connectors

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Snug up connections

Screw threaded connections together finger-tight, then twist the nut an extra quarter turn with a wrench for a solid connection.

As with end connectors, the threaded connectors on wall jacks, computers and TVs must provide a solid path for the signal. Most people finger-tighten these connections, but that just isn't good enough. Instead, use a 7/16-in. wrench to snug up the connection.

Don't use standard electrical boxes

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Low-voltage boxes are best

Mount wall jacks on low-voltage boxes. Since they don't have backs or sides, these boxes allow cable to make a gentle bend inside the wall.

The sides and back on a standard electrical box force you to bend the cable sharply inside the box. And you already know why that's bad (see Mistake No. 2). Low-voltage boxes let you make a gentle bend because they aren't really boxes at all, just frames that mount on drywall. These boxes are sold at home centers and can also be used for phone, speaker and other low-voltage wiring.

Don't use a cheap splitter

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Buy quality

Judge a splitter by the numbers. If you have cable service, buy one labeled “5-1450 MHz.” For satellite TV, look for a high end of at least 2200 MHz.

Every time you split a TV signal, it gets weaker. But you have to split the signal if you want to add a TV. Still, you can avoid poor picture quality. First, buy a splitter (sold at home centers) that can handle the bandwidth needed for high-definition television and high-speed Internet. If you get poor picture quality after installing a splitter, call your cable provider for advice (they may increase your signal strength). You can also install an amplifier to boost the signal coming from your antenna, satellite or cable service. Amplifiers sell for as little as $20 at home centers, electronics stores and online (search for “TV amplifier”). But plan to spend $50 or more to get better results. And keep your receipt so you can return the amplifier if it doesn't help.