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CellPhone Jammer

— Posted by darK troll on 1:41 am on Nov. 25, 2001

I was wondering on how to make a cell phone jammer… if possible out of a cell phone, or something portable and/or of that size…

— Posted by DogMan on 11:45 pm on Dec. 19, 2001

Sorry to say this but it can not be done…..
But you can make a jammer for all communication. i knew a guy whow did this and he stopt all com for 2 miles the was later put is jail for 7 years and is still in there. it was the size of a TV. he used it to stop all police radios so he could steal a pay phone.

— Posted by Barker on 4:02 pm on Jan. 11, 2002

HA HA 7 years!!?!?

— Posted by balor on 5:16 pm on Jan. 11, 2002

I read in the paper a couple of months ago about mobiles going off in restauraunts,cafes etc.They were wondering how to deal with the fucking nuisance that a phone ringing every two seconds is.They were on about this jammer that I think is installed or about to be installed in cafes etc. in Belgium I think.According to the paper it is possible to block mobiles locally but enabling police radios and others.

— Posted by johnny 99 on 12:16 am on Mar. 15, 2002

yea, you can jam all commo in a limited area with a device from the turn of the last century called a spark gap transmitter. do a search on google, you will come up with a couple of diferent sites that tell you how to make one out of an ignition coil. but the fcc takes a very dim view of this sort of federal offence. also dont forget that every time you turn it on you are sending out one helluva homing signal for the radio police to find you with.  

— Posted by Hergor on 7:10 am on Mar. 15, 2002

but when using a ‘spark gap generator’ you need a big amplifier ’cause the range of such a device is very limited.

also i don’t really know if this thing works for recently produced mobile phones. their frequency lies quite high.

(Edited by Hergor at 7:11 am on Mar. 15, 2002)

— Posted by Zambosan on 11:46 am on Mar. 15, 2002

A spark gap generator generates impulses, which consist of an infinite range of frequencies… but the power drops off pretty quickly for higher frequency bands.  Digital cellphones are designed to tolerate quite a bit of noise.  Most use spread-spectrum techniques, direct sequence or frequency hopping, that results in a low probability of intercept and low probability of jamming (LPI/LPJ).  Spark-gap interference messes up AM radio stations pretty well, but not an awful lot more.

The only way to really “blanket” an area is to saturate all frequency bands of interest, which requires an awful lot of power and probably several antennae.  DogMan, as usual you’re a source of lies.  First of all, not a lot of police cooperation is required to apprehend an idiot lugging a payphone.  Secondly, no device “the size of a TV” is going to “stop all com for 2 miles”.  Thirdly, even if there was such a device, no one would leave such an expensive piece of equipment behind just so they could take a fucking payphone.  If yer gonna make shit up, shoot for believable as opposed to sensational.  I’m still dying with laughter over your “atomic bomb” post.

— Posted by XxBULAxX on 6:09 pm on Mar. 15, 2002

It seems like this guy “DogMan” gets on the forum and automatically knows 10x as much as professionals. My advice on how to deal with him is don’t.. just ignore the little prick… Also, it is close to impossible to jam cellphones…{} But the average joe with no electronic experience can’t do it…

(Edited by XxBULAxX at 6:12 pm on Mar. 15, 2002)

— Posted by yourunforgivenII on 12:20 am on Mar. 27, 2002

well, since cellphones are done with localised towers, then when the person left the area of the jammer if there was one, then wouldnt it no longer be jammed ?

— Posted by Zambosan on 12:19 pm on Mar. 27, 2002

Of course.  Any electromagnetic signal will weaken by a factor of 1/d^2 over distance, and there’s also absorptive & reflective losses in anything but a vacuum.

— Posted by xenonalieninfo on 8:32 pm on Mar. 27, 2002

jamming a singal is not that hard, you just find the right frequecny you won’t and sent a bad singal, the person lessing in will get a mixed message or your singal(depending on the power and there equiment tec)

— Posted by Zambosan on 10:37 am on Mar. 28, 2002

Not exactly.  Most new personal wireless equipment these days is based on spread-spectrum protocols for exactly that reason; they either hop around on frequencies in a psuedo-random fashion (frequency-hopping spread-spectrum, FHSS), or spread the transmitted energy over multiple frequencies simultaneously (direct-sequence spread-spectrum, DSSS).  And the digital modulation techniques used (binary phase-shift keying and quadrature amplitude modulation being the most popular) are very tolerant to noise at the physical encoding layer, and higher link-layer and medium access layers add additional encoding algorithms for forward error correction (viterbi encoding, reed-solomon encoding, and more recently turbo product codes) that further increase the probability that the receiver will be able to reconstruct the data stream perfectly even if a lot of the raw bits get garbled.

— Posted by xenonalieninfo on 9:23 pm on April 2, 2002

what happens if you send a bad PAiTY(spelt wrong, number 8 on a bit, used for error checking) bit

— Posted by Zambosan on 11:40 am on April 3, 2002

Okay, this has a shred of value… that’s a little better.  Parity is about the most primitive error detection scheme you can get.  Single-bit parity can only detect single-bit errors reliably, and its ability to detect multiple bit errors goes down the toilet very quickly (in terms of probability of detection) as the number of bit errors goes up.  In wireless communications (and even most wired environments), additive noise, multi-path interference, and dropouts usually result in “bursty” errors, so multiple bit errors are the norm, not the exception.  As such, parity is not used in communications, more sophisticated algorithms like the ones listed in my last post are.  They are capable of detecting and often times correcting or at least interpolating the values of mangled bits.  With real-time voice/video transmissions, you really don’t have the luxury of being able to ask the sender to re-transmit, or you’ll get a jittery A/V signal on the other end.  Parity is still used in low-speed connections and in some memory devices, mostly for historical reasons since even a CRC is much better and extremely easy to implement in hardware with a shift register and a couple of XOR gates.  As far as the response to a bad parity bit, that depends on the protocol or system in question.  Since parity can’t tell you *which* bit changed, the only recourses are to either have the data retransmitted, or just drop it entirely if the system requirements allow for it.

— Posted by sl33p on 7:02 pm on April 4, 2002

has anyone ever heard of the magic bagg?
well i was wondering if u could cover a single cell fone with alum foil. and i wonder if it will work.

— Posted by qube on 7:39 pm on April 4, 2002

Hey d00d can u explain that 2 me? Whats a magic bagg….

— Posted by tee hee on 8:10 pm on April 4, 2002

i think I read about cell phones being used to know exactly where you are at all times by the cell companies.
I think the site was http://www.shortnews.com >(this site is a great refreshing site, if you are losing patience in media distortion and PR’s .On this site the subscribers tell the news kind of like a news forum but professional.)Anyways i am no phreaker but this is obviously conspicous and it sucks. No damn privacy!!!!!:angry:

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