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How to Use Directional Yagi Beam Antennas For Cellular Phones
What are Yagi Cell Phone Antennas?
The most powerful cell phone antennas you can buy are known as Yagi antennas after the Japanese inventor of the same name. Yagi antennas are highly directional. In other words, they boost receiving and transmitting in a very narrow band of only a couple of degrees. The more elements a Yagi antenna has, the higher the gain and the more directional it is.
DB Gain is a measure of how much an antenna boosts the incoming and outgoing signal. There are cell phone Yagi antennas that offer over twelve decibels of gain.
When used with a cell phone amplifier, which boosts the signal from your phone to three watts (the legal limit), a Yagi antenna can give you an effected radiated power of over a hundred watts. This can get you a cell phone coverage in areas where there is non with a regular antenna, such as remote cabins or oilfield locations. Typically a cellular Yagi antenna is placed up on a pole as high as possible and aimed toward the nearest cell phone tower.
How To Know If a Cellular Yagi Will Work With Your Phone
The problem with using a cellular Yagi antenna is that most carriers today, including AT&T, Verizon, Alltel, Sprint, US Cellular and others, use both 1900 and 800 MHZ frequencies. Most Yagi cellular antennas only boost 800 MHZ. What the sellers of these antennas do not tell customers is that if you have any of the carriers above and hook you phone up to one of their antennas, and if you are in an area where the system is 1900 MHZ, you will burn out the transmitter portion of the phone. This is because your phone is transmitting on one frequency into an antenna made for another, and the signal is reflected back into your phone. A SWR or standing wave resistance is created. You won't realize that you are burning out your cell phone until it is too late.
While 900 MHZ is the most common frequency you need to boost in remote areas you should have a directional antenna that works on both bands to protect your phone, just in case the closest tower is on 1900 MHZ. The 1900 MHZ towers, or PCS towers, are usually located along interstates and in cities. In some areas of the country, such as South Texas, carriers such as Verizon must use 1900 Mhz to cover wide areas because they cannot get a license for 800, as it is controlled by other carriers.
How Far Will a Cellular Yagi or Directional Antenna Boost Your Cell Phone Signal?
One thing is certain and that is you can get much better cell phone reception in marginal areas using a Yagi antenna than you could without one. What is not certain is how they will perform in every situation. In areas like deep forest, where trees block the incoming cell phone signal or in canyons, you may not be able to get a connection despite using a Yagi antenna or even a Yagi - cell phone booster combination.
Below Is an Illustration of The Radiation Pattern From A High Gain Directional Yagi Cellular Antenna
Time and Distance Limitations
There may be cases where you can get several bars on your phone using a cellular Yagi and amplifier, and still not be able to place calls. This is because of a little known phenomenon that relates to how your cell phone "talks" to the tower. With GSM, which is used by AT&T and others, there is a physical limit of approximately 30 miles that cannot be overcome due the time slot factor. Because your cell phone cannot "handshake" with the tower, or exchange small bits of data that take milliseconds, you cannot make a call. You may be able to text in some cases, but voice calls are not possible past 30 miles from your phone to a GSM tower.
CDMA, which is used by Alltel, Verizon and Sprint, does not have this limitation and it is purely the transmit power of your cell phone and the strength of the received signal from that tower that determines it you will establish a connection. It is for this reason that CDMA is the transmission method of choice in places with a lot of far flung real estate, such as Australia.
What is The Best Way to Hook Up a Yagi Antenna To Your Cell Phone?
When handheld cell phones first came out almost all of them had a small jack on the rear, next to the collapsible antenna where you attached an adapter and connected an external antenna. While some phones still have a tiny jack, located under a rubber plug, or use an antenna connection on the bottom of the phone, combined with the charger and hands free circuits, many newer phones like the I Phone do not have external antenna connections. In this case you have only two alternatives. One is to use a type of patch adapter, which you stick on the outside of the phone closest to the internal antenna. This is supposed to pick up the radiated signal and send it on down the wire to the antenna. The fact is that these work very poorly.
The best option is to use a repeater type cell phone amplifier which runs on to the Yagi antenna. Repeater types, such as the one made by Digital Antenna, pick up the signal you phone transmits using a small in-cab antenna. It then repeats your signal, at the full legal limit of 3 watts, on to the directional cellular antenna or other antennas. You just want to make sure that you use a dual band cellular Yagi since you can burn up a dual band cellular amplifier with a monoband Yagi that is made only for 800 Mhz. Dual band antennas are quickly replacing single band directional ones for remote area use. Remember to place a cell phone Yagi antenna as high as possible, use the heaviest size coaxial cable available and spend some time locking in on the strongest cell phone tower.
Drawbacks Of Direct Connect Cell Phone AmplifiersDirect connect cell phone amplifiers offer the most boost but have their drawbacks. Most direct connect cell phone amps only work with phones that have an antenna jack on the back and there aren't that many of them made anymore. Antenna connectors for a small number of phones can be found at Radio Shack in many small towns where cell phone reception is a problem. Patch type connectors, which are advertised to connect new smart phones to amplifiers DO NOT WORK. If you want to use a direct connect amplifier, you'll have to buy an old phone off of eBay and either activate it (Verizon) or put your smart card (AT&T) in it. Using a direct connect cell phone amplifier, you may be able to achieve 50 plus miles with Alltell and Verizon in those areas of the US where their systems use the 800 Mhz frequency. With, AT&T, regardless of whether it is 800 or 1900 Mhz, you are limited to 30 miles due to the way that GSM cellular transmission works. At distances past 30 miles, your phone can't lock in on the tower and make a call, even if you have 5 bars. Because of the limitations of direct connect cell phone amplifiers I recommend the repeater type amps, such as those made by Wilson Electronics or Digital Antenna. Most of these can be connected to a Yagi cellular antenna using the proper connector.
For information on "repeater type cell phone amplifiers" please refer to this article: Cell Phone Boosters