Planning the coaxial cable path
Once you've determined where to mount your antenna, the next step is to lay
out your cabling plan. You want to know:
How much cable is needed: You don't want any excess cable because
even the very best cable loses some signal strength over its length. You
also don't want to coil any cable, because that creates another electro-
magnetic field that might easily create interference.
What kind of cable is needed: There are two types of low-loss cable
that are both effective and affordable:
· LMR-400: Used as primary antenna cable. The attenuation (loss of
signal strength over distance) is approximately 6.69dB per 100 feet,
so approximately .67dB is lost every 10 feet.
· LMR-100: Used as a pigtail connecting the computer to the main
antenna cable. (Pigtails are short cables used to connect, for exam-
ple, a device with connector A to a cable using connector B. The pig-
tail would have, say, a female A at one end and a male B at the other
end.) The attenuation is approximately 39.363dB per 100 feet -- a
signal-strength loss of 1.6dB over a 4-foot length.
A typical coaxial-cable installation includes several feet of LMR-400
(larger RVs may use as much as 40 feet), with 3 or 4 feet of LMR-100 as a
pigtail, to connect the laptop to the main (LMR-400) coaxial cable.
How the cable is to be secured: Cable clamps are readily available at
hardware stores such as Lowe's, Ace, or Home Depot. I'm a big fan of the
clean and neat installation of cable, but just because it's covered up
doesn't mean you don't need to secure it the best way you can.
In the next phase of creating your plan, you need to mark where antenna
cable will run, mark the places where holes might have to be drilled, and
make measurements. Here are the basic steps I follow:
1. Gather the necessary tools: a tape measure, a pencil, masking tape,
and a quarter-inch rope or cord.
The perfect cord to use in planning coaxial cable runs -- because it's
cheap and readily available -- is clothesline. It usually comes in 50-foot
lengths and you can use masking tape to hold it in place.
2. To figure out the amount of cable that's needed, I use clothesline cord
as a stand-in for the coaxial cable and tape the cord in place.
This approach makes it easier to plan for any corners or obstacles to be
negotiated; I can try several different paths to decide which works best.
Part I: The Wonderful World of Wireless Fidelity
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