| Yagi Antenna
|The Yagi antenna is a directional antenna and should be mounted above tree lines and pointed directly to your wireless service providers nearest cell tower.
The "Boom" is the long horizontal bar you see in the image. The "Elements" are the small thin rods supported by the boom. These elements are usually vertically positioned, as seen in the image. The front of the Yagi antenna has the shorter elements and the rear has the longer ones. The difference in element dimension is small compared to those Log-Periodic TV antennas you may have seen. Starting from the rear, the boom has the reflector then always the "driven" element then from 1 to any number of "directors" usually 1 to 14. The signal output is off the front end of the boom. The signal "beam" is anywhere from 20 to 90 degrees wide with the longest or most elemented design having the narrowest width and highest gain or reach.
What Is Polarization?
Radio signals travel polarized or oriented vertically, horizontally, circularly or combinations of these. In cellular and most commercial applications signals are vertically polarized. For example, your external cellular mobile phone antenna on a car is vertically polarized. Your Yagi must be installed with its elements vertically polarized too.
Where To Mount The Yagi 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 signal has to penetrate. Wood and concrete are normally invisible to RF signals but at these frequencies gain may be reduced.
Where To Point The Yagi Antenna?
The front of the Yagi 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, you will have satisfactory results. Slowly rotate the Yagi antenna and stop every 5 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 Yagi antenna and to the back or sides. Never stand in front of the Yagi antenna because your body can greatly alter signal patterns.
Yagi Antenna Height/ Cable Length
The Yagi 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 Yagi antenna, never coil or fold up the cable. Safety Precautions These Yagi antennas, like most antennas, are made of aluminum which is a great conductor of electric power besides radio frequency energy. You can be instantly killed if the Yagi antenna or support structure being worked with touches an electric power line. Never install a Yagi antenna during rain or wet conditions. Finally, don't stand less than 5 feet in front of the transmitting Yagi antenna when using a regular 3 watt phone. Don't install the yagi antenna where the signal has to cross where people will be walking in front of or touch your Yagi antenna. While radiation dangers at low power are not proven, don't take chances with RF emissions.