focused (or dense), a directional antenna may be less affected by any
local interference.
Need to be aimed: As with a flashlight beam, a directional antenna has
to be aimed at the target. This need to be aimed -- and the fact that the
beam width narrows as the gain increases -- makes the accuracy of the
aim more critical as gain increases. Thus you may want to avoid using a
directional antenna with a rated gain in excess of 10 to 12 dBi.
After reading the preceding information, you might be all set to run out the door
in search of a directional antenna. Well, wait just a second there partner --
there's more to this story. Everything I've said about a directional antenna is
true, but (you just knew a "but" was coming, didn't you?) when you're travel-
ing, you might not be able to get a clear shot at the signal source. That's espe-
cially true if the source is coming from behind and you've got a big ol' trailer
between you and it. High trailers, especially metallic trailers, can serve as
outstandingly effective barriers to wireless signals.
You might be well advised to seriously consider choosing a less discriminat-
ing omnidirectional antenna that encompasses a much wider area. So here
are some attributes typical to omnidirectional antennas:
360-degree horizontal beam width: Because energy is being expended
throughout a 360-degree circumference around the antenna, the beam is
somewhat less efficient than that of a directional antenna. As the gain of
an omnidirectional antenna increases, the vertical beam width becomes
narrower and more focused -- but (of course) its 360-degree horizontal
beam width is maintained.
Susceptible to interference: At least it's more susceptible than a direc-
tional antenna might be in the same environment. While the hotspot
signal may be coming from one direction, interference in another area
may be picked up as well. A high-gain omnidirectional antenna is, how-
ever, less susceptible to interference than its low-gain cousin.
No aiming: The real beauty of an omnidirectional antenna is that it
doesn't need to be precisely aimed -- so it might detect signals that
would otherwise be blocked from a directional antenna's line of sight.
Choosing an indoor versus
an outdoor antenna
When you're choosing an external high-gain antenna for use with your high-
power adapter, you'll have to decide whether you'll want to use a directional
Part I: The Wonderful World of Wireless Fidelity
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