Traditional and Modern Methods of Football Signal Jamming

Those of you that are football fans probably watched the Indianapolis Colts and the New England Patriots play last Sunday. On the first play of the fourth quarter, New England Quarterback Tom Brady threw a successful 14 yard pass to receiver Randy Moss. What was interesting about this play was the crowd noise. If you watched the game on CBS you heard A LOT of noise before and during the play and a noticeable lack of noise immediately after Moss had caught the ball. Here's a clip on YouTube of the play and the catch.


In no way am I implying that the Colts cheated in any way! Crowd noise is one of the home field advantages and is an old-fashioned attempt at lowering the audio signal to noise ratio (SNR). I covered signal to noise ratio in another blog on Monday.

Here's how crowd noise reduces the audio SNR - the visiting team quarterback is calling signals and the crowd is making noise. If the signal (quarterback) strength is weak compared to the noise (crowd) the rest of the offensive team has trouble hearing the signals. The more noise the better as far as home teams are concerned - It's perfectly legal this year in the NFL with a rule change this past spring eliminating a five yard defensive penalty (rarely called in the past) for excessive crowd noise.

Let's get back to the Colts/Patriots game - was the crowd noise amplified or enhanced in some way at the RCA Dome in Indianapolis on Sunday? It appears not - the enhancement was done by CBS for the television viewers. The NFL quickly released a statement on their website, here's a piece of that release:

CBS has informed us that the unusual audio moment heard by fans during the Patriots-Colts game was the result of tape feedback in the CBS production truck and was isolated to the CBS broadcast. It was in no way related to any sound within the stadium and could not be heard in the stadium.

That takes care of the crowd noise - now let's consider the wireless communications systems used at the game. In his press conference after the game, New England coach Bill Belichick said the wireless communications system between the coaches and quarterback Tom Brady was "basically useless". Here's a quote from an AP piece published on Yahoo News:

..... Belichick said he was more concerned with communication problems he said existed between Patriots coaches and Brady.

"Basically, we didn't have a coach-to-quarterback operation, so we had to signal in all of the plays, which is unusual, but that's the way it was," he said. "What all was going on, I can't tell you, but I can tell you that, from a functional standpoint, the coach-to-quarterback was basically useless."

Here's where my mind is going...... I've written about wireless jammers over the past couple of days here and have discussed devices that are small enough to fit inside a pack of cigarettes to ones that are large enough to kill cell phones in large banquet halls. Could a fan smuggle in a jammer with some kind of directional antenna that could be aimed at the sidelines of the opposing team? I'm not accusing anyone of any kind of crime but I believe it may be theoretically possible. I also know nothing about security at NFL games and have not attended one in the past couple of years.

But...... Would a stadium security person have any idea what a jammer was?

And..... Could one be disguised and built into something like a portable TV set that I've seen fans bring to games in the past?

I do think if I was an NFL coach I'd go back to wired headsets and hand signals to my quarterback until these issues get resolved.

Jamming Cell Phones

Jamming cell phone signals is illegal in the United States but not illegal in other countries. As a result, people in the United States are finding and buying these devices on the Internet. The New York Times ran an interesting piece on November 2 titled Devices Enforce Silence of Cellphones, Illegally. The piece starts with the following:

One afternoon in early September, an architect boarded his commuter train and became a cellphone vigilante. He sat down next to a 20-something woman who he said was “blabbing away” into her phone.

“She was using the word ‘like’ all the time. She sounded like a Valley Girl,” said the architect, Andrew, who declined to give his last name because what he did next was illegal.

Andrew reached into his shirt pocket and pushed a button on a black device the size of a cigarette pack. It sent out a powerful radio signal that cut off the chatterer’s cellphone transmission — and any others in a 30-foot radius. “She kept talking into her phone for about 30 seconds before she realized there was no one listening on the other end,” he said.

I've written about wireless signal jamming in the past - specifically when I wrote about the New England Patriots video taping scandal that included rumors of wireless communications signal jamming. I have to admit, while watching the Colts/Patriots game yesterday and seeing Tom Brady struggle hearing plays using his helmet headset, jamming was on my mind. It got to the point plays were being relayed in the old fashioned way - was it crowd noise or could it have been signal jamming?

Let's take a basic look at the technology. Communications technicians and engineers are constantly aware of something called the signal-to-noise ratio, commonly abbreviated as SNR. The noise we are typically dealing with in unjammed situations is commonly referred to as Johnson or White Noise and it's always there. If systems are designed properly and when in range, communications signals are stronger than the noise and the noise is less significant because the SNR is high (think divide signal strength by noise strength). Basically, if a wanted communications signal is stronger than the noise then communications happens. If the noise is stronger than the communications signal then communications does not happen. We've all experience this in our cars while driving and listening to a radio station. As we get closer to a station signal source (antenna), the signal gets stronger and we hear the station clearer.

Now back to jammers - in simplest terms, jammers work by sending out strong signals that overpower the wanted communications signals between a cell phone and cellular antenna towers. Basically they generate the equivalent of noise at specific cell frequencies. Phones end up not communicating with the towers and users see a "No Service" type message on their phones.

A quick search of the Internet brings up a number of off-shore companies selling signal jammers. One of the more popular companies is London based PhoneJammer.com. PhoneJammer.com sells lots of different jamming devices ranging from a $149 portable jammer that runs on 9V batteries and has a range of 5m to a $3995 ultra high power phone jammer which is described as the most sophisticated digital cell phone jammer of its class, with tough die-cast aluminum casing and dual inter cooler, ideal for large hall type rooms or outdoor locations. It comes with a high gain base station type antenna.

The New York Times quotes PhoneJammer.com's site operator as follows:

"Victor McCormack, the site’s operator, says he ships roughly 400 jammers a month into the United States, up from 300 a year ago. Orders for holiday gifts, he said, have exceeded 2,000."

I'll write more about different kinds of wireless signal jamming this week. Remember - the devices are illegal in the United States.