Original URL: http://www.theregister.co.uk/2007/11/26/mobile_jamming/
Commuters shouting into their mobiles? Just jam 'em
There's just one problem. It's illegal
Column When a columnist starts off "Silent, but deadly..." you know he's trying to be funny; and Matt Rudd's  recent praise for phone radio jammers is, clearly, not based on the fact he doesn't know what SBD actually means.
Anti-social behaviour on trains these days isn't limited to producing methane; it is more commonly believed to be a problem with telephony. Rudd wrote his chucklesome piece saying that actually, you don't have to put up with people talking at the top of their voices behind you. We have the technology.
Technically, he's quite right. Phones use a very weak signal (which is why most electronics engineers don't believe they cause cancer, duh) and anybody who can transmit a slightly stronger signal on the same channel will block it. For quite amazingly large sums, if you want to impress people, you can buy a little black box that will do this, and if you want a list, try Google and ask for "phone jammer" and watch the hits pour in.
There's a small problem, which the column does mention: it's illegal. Not everywhere in the world, admittedly, and so actually making the devices is hard to prohibit; and there aren't likely to be any laws in Russia (say) to stop you from selling phone jamming equipment to Taiwan... or vice versa, come to that. And so you can get them; and if you just want utility, then you can actually get them very cheap.
Beware, because the devil is in the detail.
If you are looking for a clue, have a look at the very erudite review of phone jammers at Spy Review .
The reviewer gives the technical background first: "The jammer has three aerials to match the three frequency bands it's designed to block out. If an aerial does not match the wavelength (and thus frequency) of the transmitted radio signal, the strength of the signal can be severely limited," the article explains.
All well and good, but then it notes, casually enough: "The jammer is intended to block out the following frequencies" and lists them:
- 851 - 960Mhz
- 1805 - 1990Mhz
- 2100 - 2170Mhz
The first thing you'll note is that this should, in theory, block all UK based cellphone signals. But if you're an expert (and the reviewer is) you'll notice that the widely used European band, GSM1800 is not completely knocked out. "The first set of frequencies on GSM1800 do not fall within the specified range on the jammer. However, GSM900 and GSM1900 are completely covered by the jammer. I wonder if the jammer does completely knock out service providers using GSM1800?"
Yes, of course he would wonder because a genuine review would require a genuine test which would be genuinely illegal activity.
No such questions are suggested at PhoneJammer  where the devices are sold. Instead, it explains how useful its products are - and at prices around £2,000 - for major projects like preventing phone calls in cinemas and theatres and churches:
Introducing the ultra high power phone jammer, the most sophisticated digital cell phone jammer of its class, with tough die-cast aluminium casing and dual inter cooler, ideal for large to hall type rooms or outdoor locations (high gain base station type antenna supplied).
I'm not saying such devices aren't available. Actually, I wouldn't even try to pretend I think they aren't in use. I happen to know a cinema not far from here where, mysteriously, car alarms won't work in the car park behind the theatres, and while they do ask patrons to switch their phones off, I've yet to hear one ring. Perhaps the patrons are all saintly?
Perhaps not. Our silent but deadly social villain tells a lovely story about how he arrived at a party in an unnamed location, furious about having his train journey ruined by someone talking... (why?) and was furtively led to one side:
'You need a jammer.' With a nod and a wink, I followed the dapper man to the outer edges of the party and he began to explain. He commutes from somewhere Midlands-ish to somewhere Birmingham-ish. When an annoying fellow commuter begins to prattle, he simply flicks a switch and the prattling ceases.
How seriously should we take this James Bond narrative?
Well, in one sense, entirely seriously. The devices do exist; and prices don't have to be measured in the thousands, or even the hundreds. There are toys which cost £50 ($100) and will knock out phone conversations within five yards. And you can order them.
Which leads us to the mystery: why Rudd made such a big fuss about the problems of finding suppliers. It's really not a problem and Google will point you at dozens of suppliers - but the humourist (perhaps) made him go on about how he broke the unspoken code of jammers, by asking to speak on the record. And after that, he laments, nobody would tell him anything. Including where to find one...
OK, back to the spy review, and maybe we can find what the real problem is. The real problem might just be "does it work?"
That's the problem with buying illegal products. You send your credit card or PayPal details; and you get a little black box in the post. Written on the side is "Phone Jammer" and inside the box is a Japlish instruction manual which says: "Press button B" and, well, that's that.
You press button B. The conversation which is so irritating your sensitive little soul, continues unabated. Your jammer: is it under powered? not close enough? or... horrible thought! - have you been taken?
There's not a lot you can do if you have been, is there? What are you going to try - complain to Ofcom? I don't think so... Trading Standards? "I've bought this illegal product which is impossible to test without breaking the law, and I suspect it doesn't work..."? No, I think best not.
And, of course, there's the final ignominious possibility... that your jammer works just fine - but that the loud-mouthed person on the train is, in fact, an unemployed PR bunny who can't afford a real mobile phone right now, and is actually just making loud noises to impress fellow travellers.
Oh, yes, it does happen. You can actually buy dummy phones for that purpose. Just don't ask for your money back if they don't work, OK, yah? ®