*Cell Phone Site: 10 Cent Tour*
By: Jaden
18 May 2008

Cellular telephone towers are everywhere these days. Here’s what is all looks like close up.

Cell sites are located on towers, water towers, roof tops, hidden in church steeples and several other places. They are actually a rather simple operation. Cell phones are nothing more than full duplex radios which means they transmit and receive at the same time, which allows them to work like a normal land line telephone.

Let’s start with the best part.

Antennas!

4 sites on this tower---------------------------150’ up----------------------------------------------On a Hilton

Each level of antennas is a separate carrier. Verizon, Alltel, AT&T, T-Mobile, US Cellular or whoever.

Cell sites require maintenance to repair broken antennas and connectors and anything else that goes wrong. Sometimes when a site is swept (lines and antennas tested for efficiency) they fail and need repairs.

Hanging 250’ above the ground---------------------------HEY RUBIES!!!----------------------------I’m in there somewhere

There are different brands and styles of antennas out there, but they all essentially work the same. When in operation they are set up in to 3 sectors. Alfa, Beta and Gamma. If you look at a site, you’ll notice that there are 1 or 2 antennas pointing in 3 different directions. Sometimes there’ll be 3-4 antennas per sector. Each direction is a separate sector.

Some antennas have two pieces of transmission line connected to them while others only have one. You’ll notice above that there’s two transmission lines going to that one round antenna. That’s because the antenna is designed to transmit and receive at the same time. In the left picture you’ll notice there are two antennas to the left. Each of those is fed by one line. One antenna receives and the other transmits.

When we install the antennas we have to make sure that they are level. Then an engineer does his super complicated algebraic calculations and tells us exactly what direction they have to be facing and how many degrees of down tilt is needed. For high mounted antennas, they are tilted down slightly so that the signals reach the ground. The round one pictured above can be down tilted electrically from the ground. The two big ones shown need to be done on the tower.

These antennas have a 65 degree beam width.

http://www.hdtvprimer.com

Transmission line

Typically the lines will be 1 5/8” or 2 ¼” diameter. Because of the frequencies that cellular phones use the larger low loss line is necessary to make those 200 and 300 foot runs. They terminate in to ½” low loss line which connect to the antenna and also to the equipment on the ground.

Main line connected to jumpers-----------------------------1 5/8”

Unfortunately I wasn’t able to get any pictures of the brains behind the operation. It is housed in the cabinet pictured below.

A few thoughts...

Cellular sites can be controlled remotely. The site can be shut down completely from a location 100 miles or further away at any time.

An engineer can also control a site while sitting in a vehicle.

Cellular sites also utilize the GPS system. If the GPS system is off line, guess what else won’t work.

Some sites do not have back up power.
Jaden


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