How Can You Gain From Gain, When You Don’t Know What I’m
Talking About?
Hello for 04-2000
By: Mike Lipshultz
Mike@biznetonline.com
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How Can You Gain From Gain, When You Don’t Know What I’m
Talking About? |
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If you have ever shopped for an Antenna (for a TV, Cell
Phone, CB Set, or almost any other “Radio” type device) you probably have
heard the word “Gain”. Like
“this antenna is high Gain”. Now
most people think any antenna that is a “High Gain” is better then one that
is not. But in reality the best
antenna for any given device is the one best suited for the area that it will be
used in. In fact a “High Gain”
antenna dose not increase the strength of the signal or make it stronger in any
way. It just “receives” the
signal in a different way than a none gain antenna.
And that is not always better.
Now that I have you totally confused let me give you some
information taken straight from the web site of a company called Andrew.
Andrew (http://www.andrew.com
) is a company that, among other products, designs and manufactures antennas.
Their site has the best explanation of “Gain” I have ever seen.
So here it is:
Q. What is gain?
A. Gain is a measure of how much of
the total power of the antenna is radiated. Gain does not equal power. The power
of the signal is determined by the phone. There are generally three types of
gain for cellular and two types for PCS. It is easiest to think of a fully
inflated beach ball when thinking about gain.
0 dB means that equal amounts of the signal
are being radiated horizontally and vertically. Think of the beach ball when it
is fully inflated. It is the same size all the way around. This type of antenna
is good for use in urban areas with tall buildings and obstructions.
3 dB means that more of the signal is
radiated horizontally than vertically. Again, think of the beach ball. Instead
this time, you place your hands on the top and bottom and apply pressure. The
shape of the beach ball is flattened, but it has not lost any air. The same
applies to gain; the signal strength is not changed, just flattened. This type
of antenna is good in suburban areas. This is considered the most universal
antenna.
4 dB means that most of the signal is
radiated horizontally and very little is radiated vertically. Again, think of
the beach ball. Apply even more pressure to the top and bottom. This will
flatten the ball out even more. This type of antenna is good in rural areas.
Q. What type of gain is
best?
A. There is no best type of gain. It depends on where you will be using
the antenna. If you are looking for an antenna to use in all areas, we would
recommend the 3 dB antenna. If you are usually in a city or an urban area, 0 dB
antennas are good. If you live in a rural area, 4 dB antennas are better.
Q. Some antenna gain measurements are listed as dBd and some are listed as dBi.
What is the difference and which is better?
A. All antenna gain measurement are relative to something else. DBi is a
measurement relative to a theoretical isotropic radiator. This is considered, to
a point, antennas that radiate in a perfect spherical pattern of energy. An
easily visualized, but impossible to build device.
DBd is measured in relation to a center-fed
half wave dipole antenna. This is one of the simplest antennas to construct and
is a convenient standard of measurement. At Andrew Wireless Products, all
antennas are measured in dBd. Don’t be fooled by some listings that give a dBi
measurement; many manufacturers use dBi to get a higher gain number for their
antennas. In reality, the gain measurement is lower than stated.
Now hopefully you have a better understanding
of just what “Gain” is. Now
check out Andrew's enterer Web Site at: http://www.andrew.com/home/default.asp
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