Coax, Splitters and Amplifiers

Most reception problems on cable and antenna systems come from the wiring inside the home. A few basics about coaxial cable, splitters and amplifiers go a long way toward a clean signal on every TV and tuner.

Coaxial cable and connectors

TV and cable systems use 75-ohm coaxial cable, most commonly RG-6 for runs inside a home, with screw-on F-connectors. Keep these points in mind:

• Use 75-ohm cable and fittings throughout. Mixing in other types causes reflections and loss.
• Make sure connectors are fully tightened and properly attached to the cable. A loose connector lets noise in and signal out.
• Avoid sharp bends, crushed cable and staples driven through the jacket.
• Longer runs lose more signal, and the loss is greater at higher frequencies, where many digital channels sit.

How much a splitter costs you

A splitter divides the signal between outlets, and each output gets less than went in. Typical figures from one manufacturer's specification sheet, for the 54 to 550 MHz range:

Loss is higher at the top of the band. Near 1 GHz the same sheet lists roughly 4 dB, 8 dB and 12 to 13 dB. Splitters in series add up: a 2-way followed by a 4-way costs about as much as an 8-way.

Good splitting practice

• Use the fewest splits that serve the outlets you actually use.
• If one tuner needs the strongest signal, such as a network tuner feeding several TVs, put it on the first split.
• Cap unused splitter outputs with 75-ohm terminators.
• Use splitters rated for the full frequency range of your system.
• Replace old, corroded or very cheap splitters.

When an amplifier helps

A distribution amplifier makes up for splitter and cable loss so that more outlets get a usable signal. It cannot fix a signal that is already noisy, because it boosts the noise along with the signal, and every amplifier adds some noise of its own. Too much gain can also overload tuners.

• Measure or check signal readings before adding one. If levels are fine, an amplifier can make things worse.
• Place it before the splits, close to where the signal enters.
• For cable service that includes internet, use an amplifier with a return path for upstream signals, or keep the modem ahead of the amplifier. Your provider may have rules about amplifiers on its network.
• For antennas, a preamplifier at the antenna helps on long cable runs. Near a strong transmitter, the FCC notes that removing amplifiers or adding an attenuator can cure overload.

See Cable Signal Levels and Troubleshooting for what the readings mean.

Sources

• Primex coaxial splitter specifications
• HDHomeRun: Signal Strength and Quality troubleshooting
• FCC consumer guide: Antennas and Digital Television