Is the Philadelphia Cell Phone Jammer a Hero or Pest? [telecom]

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Is the Philadelphia Cell Phone Jammer a Hero or Pest? Alissa Skelton

No service? Maybe you've been zapped by a cell phone jammer.

A Philadelphia man has stirred up controversy after he frequently used a device on a public bus to create a cell phone dead zone.

A reporter for "NBC [TV Channel] 10" in Philadelphia recently tracked down the man, who was using a cell phone jammer on the bus to block riders' cell phone reception. His reason -- he didn't want to listen to other people's phone conversations. He says he turns on the illegal device whenever other passengers talk too loud and bother him.

The man, identified as Eric, told NBC reporters: "I guess I'm taking the law into my own hands, and quite frankly, I'm proud of it."

A jammer typically looks similar to a walkie-talkie and has multiple antennae pointing out of the top of the device. Its job is to jam, block or interfere with wireless communication including Wi-Fi, cell phone reception, GPS and police radar.

Section 302(b) of the Communication Act of 1934 [PDF] prohibits the "marketing, sale or use" of jammers. The federal government and companies contracted to do federal work, typically related to homeland security, are the only ones permitted to use jammers. Like many uninformed people who have jammers, Eric said he thought a jammer was legal to use.

"We are troubled by the reported incident and are looking into it", Michelle Ellison, Chief of the Federal Communication Commission Enforcement Bureau, said in an email regarding the Philadelphia incident.

Although the device is illegal, bus riders aren't the only ones who have wanted to shut people up using a jammer. The FCC has investigated the use of cell phone jammers in schools and theaters. Some administrators apparently think a cell phone jammer would be an easy way to stop students from using their cell phones during school hours. Theaters find cell phone jammers appealing to prevent people from using phones during shows.

"While some people who use jammers may think they are only silencing loud conversations or disabling unwanted GPS tracking, they could also be preventing a scared teenager from calling 911, an elderly person from placing an urgent call to a doctor, or a rescue team from homing in on the location of a severely injured person", Ellison said. "The price for one person's moment of peace or privacy, could very well be the safety and well-being of others".

Jammers are a problem because they block licensing frequencies that are not owned by the jammer and it's illegal to interfere with any licensing frequency. Jammers can block signals within a few dozen to hundreds of feet. The FCC is most concerned with jammers blocking emergency responders communication with callers.

People in the U.S. typical buy jammers online. The FCC is trying hard to prevent other countries from selling and shipping jammers to America, but some jammers slip through the mail. The UK, Canada, Switzerland and Australia also don't allow cell phone jammers.

In October 2011, the FCC warned 20 online retailers about the illegality of selling and marketing signal jamming devices to Americans. But, with a quick Google search away, an American can order a cell phone jammer online.

"Our actions should send a strong message to retailers of signal jamming devices [that selling them] in the U.S. is illegal and that the FCC will vigorously prosecute these violations", Ellison said in a press release.

The U.S. tries hard to keep jammers out, but, the network blockers can be manufactured and exported in the U.S. The FCC said it isn't aware of any cell phone jammer manufacturing violations in the U.S.

Reply to
David Clayton
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Neither: he's just human.

I applaud him. His reactions were as predictable as the fistfights that broke out on public buses and trains when "Boom Boxes" were introduced: riders who were brought up to follow the rules of common courtesy are entitled to be offended when rude and selfish people arrogate the privilege of intruding on others' thoughts and personal space.


Reply to
Bill Horne


I first read about this specific scenario in Ray Bradbury's short story "The Murderer", published in his collection "Golden Apples of the Sun".

It was written in 1953! Bradbury accurately predicted the "all chatter, all the time" culture which would arise from having ubiquitous personal communication devices, and the fact that some people would find the constant babble-babble-babble to be quite maddening and would strike back at it.

Reply to
Dave Platt

Per David Clayton:

Sounds like an idea for restaurants. Maybe a "Cell-Phone-Free" area and a regular area.

Reply to
Pete Cresswell

I have a different solution. I hold up my antique flipphone, and tell the gabber I record people for my "What people say in public" website......

Reply to
David Lesher

I have to wonder, does the Communications Act only cover active devices, e.g. something that broadcasts a signal? What is to prevent a business from putting a grounded copper mesh throughout a room. That would blot out signal too.

At my last place of employment we had a quiet box. it was about the size of a shoebox and had a three prong cord out the back. Inside was totall covered in copper mesh, tied to the ground conductor on the power cord.

Theoretically it should work. It's how we found out that the outlets on our desks were tied to the UPS and there was no real copper ground. Wooops!

***** Moderator's Note *****

The FCC regulates "Incidental" radiators, such as the local oscillators in receivers, computer timing chips, etc., as well as licensed services.

IANALB, AFAIK, it's legal - although prohibitively expensive - to cut off cell signals in a private building. Passive shielding, which forms a Faraday cage, would be effective. It's also possible to use electrostatic shielding, but that costs a lot too.

Bill Horne Moderator

Reply to

It's not necessarily -that- expensive.

Circa 40 years ago, a bunch of volunteers (me included) did the Faraday cage thing to a church sanctuary. 'Wallpapered' it with Reynold's wrap, followed by a skim-coat of plaster, and repainted. Fine-mesh wire screens over the windows completed the cage. The doors were metal-core fire-rated, so all they needed was 'straps' across a hinge, to connect to the foil shell.

It wasn't a "perfect" cage, but it worked "well enough" to keep 'interference' (over-modulated, over-powered, CBs, mostly) out of the audio system.

Reply to
Robert Bonomi

Yes, and that is legal and reasonable, and folks do it. It's harder to do with cellphones since the wavelength is so short, but it's done.

that people trust them for emergency communications in the first place. However, the cellphone jammers cause a lot of collateral damage. I have seen several instances where they have caused interference to 950 Mhz broadcast auxiliary services.

The cheap jammers sold on ebay and dealextreme are just broadband noise sources that cover the cellular bands and sadly they cover a whole lot of other stuff as well.

The _smart_ way to jam cellphones is to pretend to be a cell tower. You advertise a connection, then you refuse to complete a call. This can be done with very low power levels (probably levels legal under Part 15 even) and very effectively. Unfortunately nobody makes a cheap device to do this, although it's only a matter of time.


Reply to
Scott Dorsey

Some of the cellular providers themselves sell a gadget that allows you to create your own "microcell" using your landline. Then all you would need is to "forget" to plug the gadget into the landline. [If you're a business and feel the need to allow 911 calls, just plug it in through one of those Radio Shack restrictor gadgets and program it to allow no number but 911.]

Of course, since the "microcell" is meant to be used in places normal cell service doesn't reach, it's probably very low-power and won't prevent the cell phone from finding other towers -- unless you also use a Faraday cage.

Then there's the more general problem that most cell networks no longer let users of other networks "roam" on them, because doing so would defeat their competing claims to have the best coverage. (Not to mention that there are incompatible technologies in use, CDMA vs TDMA vs GSM and whatever else.) Both of which mean that some phones won't even see your "cell tower", so if you care about that, you'd need more than one.

Reply to
John David Galt

This brings up an interesting point about emergency communications. The Providence, RI police department recently upgraded their radio systems. By "recent", I mean within the last few years.

A couple [of] weeks ago I was at the West Broadway Neighborhood Association meeting [where] Bill Trinque, Director of Commuications, [was] presenting.

He handed out a presentation and I start paging through [it]. I noticed that their new trunked radio system is APCO P25 compliant.

Some time ago, HackADay had posted a video on how P25 was hacked with a IM-Me(1) toy and a power amplifier. What it does is break the encryption so they're forced to transmit in the clear.

Better yet, with a Software Defined Radio (SDR) you can actualy get right on the APCO P25 systems and shut them down.

Now SDR's arent' cheap. But recent developments have implemented a n SDR in a Field Programmable Gate Array (FPGA). So the price has dropped and you can render emergency comms useless with < $200 worth of gear.

So there is no secure radio system for public safety that hasn't been fully compromised.

It all gets down to marketing. I'm sure Motorola made claims of the security of APCO P25 and the comms and police guys just ate it up.

***** Moderator's Note *****

This subject covers a wide area, and some of it is outside the telecom range. However, it /is/ important to realize that cell phones aren't nearly as reliable as some people think.

The point is that our public safety radio systems /and/ the cellular network /both/ depend on an environment without deliberate jamming, DOS attacks, or simple eavesdropping: in other words, they depend on everyone being willing to play nice. This lack of surviveability is going to become a greater issue as time goes by, because lawbreakers of all kinds will find the weaknesses and exploit them to disable cell phones or Public Safety radios.

The intense reaction I got after my previous note on the subject of the Philadelphia jammer points out a central failing in the cellular networks, and that is that cellular users are assuming that radio transceivers are as reliable as wireline phones. That's just not true, and cellular customers need to prepare for failures of their phones, or of the cellular system, if they are to have reliable access to help in an emergency.

  1. The "IM-Me" toy appears to be a short-range radio device that allows children to send and receive instant messages through a home computer.

The site that describes the "Denial of Service" attack is at

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Bill Horne Moderator

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