How Cell Towers Work
That mobile phone in your hand is a stunning piece of technology that’s almost completely useless without a network to power it. When you’re at home or in the office that’s taken care of by Wi-Fi. But when you go out into the world you need a cellular network to keep you connected that’s why you see cell towers all over the place these days. But the most interesting ones are those you don’t see. I asked AT&T to take me on a tour of two of them one in a church steeple and one on top of a mountain and to my great surprise they said yes. So join me to learn about the network behind your phone on the Mr. mobile tower tour.
Duxbury massachusetts is home of excellent oysters, beautiful coastlines, and Shakespeare productions featuring familiar youtubers. Down the road from all that is the first parish Unitarian Church built in 1840. Nothing seems out of the ordinary as you cross the parlor and pass the pews in the meeting house. But when you head up into the Attic you find more cables than any church should need. It’s nothing nefarious, though these are the conduits feeding the cell tower or more properly the cell site hidden up above, obscured in the steeple itself to preserve ducks buries bucolic landscape.
We follow the cables up some narrow stairs, and I do mean narrow. The hard hat isn’t just for looks. Then we come to the bell tower. Yes the Bell is real, and yes, it still works. Now we’re pretty high above the ground at this point but not quite far enough up to be optimal for the kind of coverage this site needs. So it’s up an even smaller ladder to the base of the steeple itself. This is where the magic happens.
Magic you can hear on the audio feed here that’s the sound of one of the cameras poorly shielded components reacting to the radio-frequency energy up here. And while that might sound scary, it’s actually safe. The workers who have to come up here to service the equipment are safe because they follow strict procedures and the people down below in the church are safe for two reasons.
The first is called the oil rig effect. The antennas up on the steeple aren’t pointed straight down but outward. Which makes sense if you think about it. The second reason is something called the inverse square law. See, radio frequency energy drops off with distance, and it does it fast up here in the steeple. I’m standing about ten feet from one of the antennas down at ground level about 50 feet away. The RF signal is sixteen times weaker. This is one of the reasons carriers need to build so many cell sites to cover a given area. The further you get from a tower, the harder your phone has to work to stay connected to it. But the same reason this entire church steeple had to be replaced with a fiberglass replica. Which is why you can see the Sun glowing through it.
Here fiberglass is more transparent to radio waves than wood. It’s all about getting the strongest possible connection to your phone. But the radio side is just part of the story. The data packets that flip back and forth when you send a text message or subscribe to a YouTube channel – well they have to traverse the internet. And to get to it landlines are still usually the most efficient way. So we follow the conduits back down the steeple through the church and out back to the equipment shelter. This is basically a concrete Shack where the connection to the landline network happens .
It is what’s called backhaul, and these days it’s all done with fiber. You ever wonder what happens if the power goes out? Well that’s where this rack of lead acid batteries come in. They provide an uninterrupted power supply in the event of an outage. There’s also a diesel generator outside with enough fuel to power the site for about a day. Generally that’s more than enough to last through a storm in this part of the country. Speaking of storms this cell-site doesn’t worry about them much. Tucked away as it is inside that cozy church.
Well I wanted to see a tower that was a little more rough and tumble so I woke up early one day and drove and drove and drove up to the White Mountains of New Hampshire. Specifically Mount Washington, the highest point in the northeastern United States and 20th century record holder for highest wind speed ever recorded. In fact, as I wrote this script the mountain had just broken
another record for coldest recorded temperature at the summit. At minus 34 degrees Fahrenheit! Well that’s why I went up there in August on what turned out to be a gorgeous day.
It’s still a treacherous ride up the incline though so at 2700 feet I traded in my rental car for more appropriate transportation. It took about 45 minutes to chug the remaining 3,500 feet to the summit. Much of it at angles almost too steep to stand, but I hopped off at the very peak of Mount Washington. The weather was still excellent and the views were amazing. The climate was so good during my visit, in fact, that it was hard to imagine the kind of violent storms I’d heard about. Until I rounded a corner and saw this. This is not the tower I came to see – it’s a microwave transmitter for backhaul.
The cover was made of fiberglass and it was almost totally demolished. As I may have heard around the mountaintop. I saw several of these things: fiberglass and canvas alike. Just ripped wide open by the punishing weather. Here some were just plain missing. Now I had assumed that one of these huge structures was the AT&T site. But now these are actually old school. They’re FM transmitters for radio stations WP K Q. In fact, the tower I came to see is this humble little stovepipe. This was a pre-existing structure that AT&T acquired, it’s history stretching all the way back to the 60s when it was built as a transmitter for TV station WMTW.
Well it’s been here ever since so apparently these cable stays are indeed as strong as they look! Remember all the antenna equipment we saw up in the steeple at Duxbury? Well imagine all of that crammed into this. There’s not quite as much gear in here since it’s just the one carrier. But it’s still a densely packed monolith of machinery. The mast is actually only part of the site, covering lands south of the mountain.
The northern reaches are taken care of by a dedicated sector built onto the site of the observatory. It looks much more like the antennas you’re probably used to seeing on towers and buildings. It’s pretty awesome following the waveguides into the Yankee building. We can see that the equipment shelter looks much the same as the one down in Duxbury but a little more Spartan. Well because it’s at the top of a mountain this site doesn’t have the kind of fiber backhaul to connect it to the landline network like Duxbury does. Instead it relies on microwave backhaul.
Remember those beat-up antennas and this particular installation hasn’t yet been updated to support LTE so for the moment this is one of the few AT&T sites left in the whole country that doesn’t have it the company tells me it’s planning an upgrade for this spring as soon as it’s safe to work up on the mountain again at which point even this tower will be an LTE site. Both of the cell sites I visited do the same job filling up that signal bar on your phone. But each has to deal with its own particular challenges.
To do that down in Duxbury keeping people happy meant refitting half a church so folks could preserve the look of their town instead of adding a cell tower up on Mount Washington aesthetics are secondary the primary concern is keeping the tower upright and broadcasting even as punishing weather pummels the site nine months out of the year there are a great many more challenges to running a network from capacity concerns to roaming agreements and maybe I’ll take a closer look at those in a future video but even putting those extra hurdles aside I came away from my double tower tour with the renewed appreciation for how much thought and sweat goes into the networks that keep you connected folks.