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| Yagi Antennas |
We recommend the Yagi
Panel antenna only for more remote areas. It's not a
easy to install and set up as other antennas. It's a
directional antenna so it must be mounted permanently on
a pole. You'll have to play around with aiming it in the
direction that gives you the best results. Get more info
on Yagi Antennas Here.
The word is the name of one of the Japanese inventors of
these directional antennas. The other inventor's name
was Uda so in technical circles these are Uda-Yagi
antennas in honor of the inventor team. The invention is
from the early 1900s.
While there is a multitude of directional antenna
designs in use today, the Yagi is the most popular, well
known and most seen. Some people call these "beam"
antennas, namely CBers and Amateur Radio Operators.
Note: the rooftop TV antennas seen
all over the US are a cousin of the Yagi design but are
called Log-Periodic because they are quite different in
serving a huge number or width of frequencies. |
 How
Do These Antennas Achieve So Much "Gain"?
Basically they are directing a major or almost their
entire signal strength in just one direction instead of
dispersing all around a 360 degree circle. All those
single element whips and rods on cars, boats etc are
omni directional, doing the 360 degree job. Zero
(unity), 3, and 5db gain are the typical numbers for
those. Usually the taller they are (for a given
frequency) the more gain is laid out on the horizon,
where it is needed.
What Is "Gain"?
This is the common term used when measuring decibels
(dB) to determine the effectiveness of an antenna in a
given direction or plane. Simply put, it is the measure
of the intensified signal where it is wanted or needed
because antennas cannot create gain. The antenna is
designed to manage the power in the wanted direction and
thus reduce it in unwanted directions.
What Is Polarization?
Radio signals travel polarized or oriented vertically,
horizontally, circularly or in combinations of these. In
cellular and most commercial applications signals are
vertically polarized. Your cellular mobile antenna on
the car is vertically polarized, for example. Your Yagi
must be installed with its elements vertically polarized
too.
Where Can I Mount The Antenna?
The available length of your feeder cable may determine
your mounting spot and cable length considerations will
address later. Otherwise any vertical or horizontal
pipe, roof edge, wall, window sill, balcony railing or
fence post can be used. Also, inside-attic hidden
install is acceptable as long as there is no metal in
the roof that signals have to penetrate. Wood and
concrete are normally invisible to RF signals but at
these frequencies (824-894 MHz) gain may be reduced.
Where Do I Point The Antenna?
The front of the antenna has to be directed at the
target, the cell site or repeater tower or other user.
It is best to use a map and compass and knowledge of
target location but usually you can locate the target if
it has a signal being sent to you. By simply rotating
your Yagi until best signal is found then centering on
the estimated location, satisfactory results may be had.
Slowly rotate the antenna and stop every 10 degrees.
Record signal levels. Note the peak and decline
positions and soon a center can be figured out then
tighten the mounting bolts. Be sure to stand at least a
couple of feet away from the antenna and to the back or
sides but never in front of it. Your body can greatly
alter signal patterns.
ANTENNA HEIGHT/CABLE LENGTH
The antenna needs to be mounted as high and in the clear
as possible. But there is a point at which increasing
height to gain 1dB can cause an extra 3dB in cable
losses. So good thinking must be utilized when deciding
when more height is needed and how much longer the cable
will be. On the other hand, if excess cable length is
present, either remove it or run a long path to the
antenna, never coil or fold up the cable.
SAFETY PRECAUTIONS
These, like most antennas, are made of aluminum, a great
conductor of electric power besides radio frequency
energy. You can be instantly killed if the antenna or
support structure being worked with touches an electric
power line. Never even think of installing an antenna
during rain or wet conditions.
Finally, don't stand less than 5 feet in front of the
transmitting antenna when using a regular 3 watt phone.
Don't install the antenna where the signal has to cross
where people will be walking in front of or touch your
antenna. While radiation dangers at low power are not
proven, don't take chances with RF emissions. |
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Other Antenna
Types
Dual Band,
Single Band, Glass Mount,
Wilson Trucker |
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