http://groups.google.com/groups?q=%22cell+phone+jammer%22&hl=en&safe=off&rnu m=3&ic=1&selm=3304cc3b.4002494%40news.erols.com From: user@lost.in.the.net (user@lost.in.the.net) Subject: HOW to BUILD A CELL-PHONE JAMMER!!!!!!!!!!!!!!!!!!!!!!!!! Newsgroups: alt.radio.pirate Date: 1997/02/14 On 7 Feb 1997 03:28:00 GMT, jlundgre@delta1.deltanet.com (John Lundgren) wrote: >Nonnaya Bizinus (NOYB@NOYB.NET) wrote: >: I would like to be able to build a cell-phone jammer to stop idiots >: from dividing their attention between talk and traffic. Can anyone >: >The problem is that there are very many channels in the mid 800 MHz >band. You could make an oscillator that would jam one channel, but you >would have a hard time jamming all of them at the same time. I think >there are 120 channels or so. But not all of them are used. And if you >jam the data channel, someone may get very angry about it. > > >-- Spark transmitter. An auto ignition coil, a cellphone antenna and a piece of antenna wire. Mount spark plug in bottom of coffee can, connect ignition coil to plug and ground to can. strip off about 8 inches of the shield braid on the cable, wind center conductor into 2" loop, solder center conductor to ground braid, use a couple wire ties to keep the loop in a coil shape. Place coil over spark plug tip in can, Don't let coil touch spark plug anywhere. Use a "Door Buzzer", the mechanical type, not an electrical one, (a hardware store usually carries one) in series in the power lead to the coil. Recommend you cover end of coffee can with metal lid, bring antenna lead out through small notch in lid. Put cell phone antenna on car. See someone talking in stead of driving? Turn on power, buzzer provides pulses to coil, coil provides spark, antenna lead coil around plug picks up spark signal, antenna roughly tunes available spark energy into cell band. and cellphone user channel dies. Works for about 200 feet in mine. *************************************************************************** http://groups.google.com/groups?q=%22cell+phone+jammer%22&hl=en&safe=off&rnu m=7&ic=1&selm=38414a2a.11408418%40news.pacbell.net From: mark (mark@netannounce.com) Subject: Re: Cell phone jammer?^ Newsgroups: sci.electronics.equipment Date: 1999/11/27 start with the ARRL handbook and look up RF amplifiers..then adjust the specs to meet the transmission freq of the cell phones (i dont know what that is) and you have a portable jammer. you just need something to "transmit" and probably a signal generator will do that > > >Alex Hornkohl wrote: >> >> Any thoughts on where to start? I'd like to create a transmitter that >> would "jam" cellular phones. >> >I know my computer works pretty well. *************************************************************************** http://groups.google.com/groups?hl=en&safe=off&th=f047d15e6e663c7b,10&rnum=5 &ic=1&selm=iv5v3s8r7ar8s1342mvf816u2v8ditqd91%404ax.com From: krackula (krackula@i.am) Subject: Re: Cell Phone Jammer Newsgroups: alt.phreaking Date: 1999/11/27 hypothetically speaking .... analog cellular communications are fairly easy to jam using highpower carriers and pulse FM modulation . FM receivers have an interesting tendency to home in on the strongest signal in the bandpass ... ! BUT .... spread spectrum and all its variants ..... which the " digital " cellfones use, are a different story altogether. This type of modulation , the spread and the time/freq division , all , are, by design ... mostly immune to jamming by ordinary means. There is a general tendency , in these SS or TDM/FDM devices ( digital cellfones ) that they are desensitized by strong local carriers ..but not usually jammed by them. To successfully jam a ( say ) tdm or pcs type signal , you need both locally high power and a modulation scheme that mimics the " particular " type of SS device that you intend to jam. You would have to generate a PIN modulated device code with a similar encoding scheme / bandwidth that the Rx ( that is to be jammed ) expects to see. Cheap ( ha ) and dirty devices can use the old ( microwave ) ploy of retransmitting a received signal with a modified modulation scheme applied to the retransmitted signal. The microwave ( radar ) jammers used a signal " chirp " that defeated the pulse timming abilities of the transmitter/Rx..! This is not a usable methodology for SS/TDM ..!! You would have to add ( instead ) a bogus but believeable ( to the SS/TDM Rx ) PIN pulse coding that the RX would " see" ( the key word here ) and react to. Most modulation schemes ( not to mention just plain FM modulated carriers ) are NOT seen or even noticed by the SS/TDM Rx ... !! This an interesting but revolutionary result of the new equipment circuit design. Really successful digital ss/tdm-fdm jammers would not only mimic the bandwidth ( a product of the encoding process ) ..but also transmit applied spread modulation of the actual type used by the system to be jammed. These applied pulse strings would be the HIGH coincendence strings ... ordinarly NOT used by the design of the normal modulation decode scheme. These code strings are accepted by the Rx to a small degree and are tried to be decoded ......not actually being the code string wanted ( by the Rx ) ..the RX rejects them and returns to listening for the proper strings ...!! Keeping the Rx tied up with these partial decodes , combined with the strong local signal strenth ( which basically forces the Rx to pay attention to you .... before others ) .... Would constitute a successful jamming exploit. There are numerous different kinds of modulation schemes within the SS/TDM/FDM general types .... and equipment capable of accessing the actual signal to be jammed ( for bandwidth/modulation scheme ) , very rapidly , would be necessary. One shortcut ...used by the mideastern jammer makers ..is to make them in advance ( at least ) for specific types of modulations and freqs of usage. ( ie 1.9 gig PCS , 900 mhz SS, 870 mhz FDM or TDM ) Its a very complex subject with enormous ( amounts of ) variables to deal with to be successful. Actual possesion of equipment or even the ( successful ) technology methodology would be of enormous value to drug lords, terrorists, and most 3rd world countries that want to jam the Military communications of ( say ) western Europe or the USA .... !! Consider what lengths the ( say ) USA might go thru to prevent a working design or apparatus from hitting the streets, so to speak. Consider this and you will see what a serious deal all of this gets to be and how much many countries have riding on preventing this technology from being " hacked ' .... figurativly speaking... !! Way kool stuff ...but worth considering the unusually high risks involved ...!! Krackula all USA ( mostly ) aircraft and most ground,ground/air communications military communications systems uses point to point and direct LOS ( low orbit satellite ) Spread spectrum ground/sat/ground communications technology , nowdays. New communications methodologys using 5gig and 10 and up freqs and revolutionary NEW modulations ( that , even to SS Rxs ) sound like noise .. ( not to say that SS doesn't ) and which are so advanced they can actually tell if someone is trying to eavesdrop on them ..exist and are being readies for field testing and use. This " stuff" as advanced and radical beyond Spread spectrum ....as SS is beyond ordinary FM communications. ( SS signals can not even be heard in any type of scanner that can be bought in a store .. ) Its' not Kansas anymore Toto ... *************************************************************************** Actually, raw power jamming will NOT work well with CDMA unless the power level is exceptionally high. A typical base station ("cell site") can put out between 150W and 200W (continuous) and the power is dynamically adjusted on a PER CALL BASIS. In other words, each call has its own power requirements. The adjustment is made several times per second (it's based on "inner loop power control" and "outer loop power control" -- see the IS-95 specs for contemporary requirements). Furthermore, for CDMA, you'd need a barrage jammer and you'd need to be able to jam all three faces of the cell. To give you an idea of the problem you'd face: the digitized voice signal is multiplied by a unique Walsh function (look at it as an orthogonal polynomial with outputs +1, -1) at a high frequency (this spreads the spectrum). Forward error correction information is attached, the signal's interleaved, and the whole signal's scrambled with a different Walsh function, again. The reverse operation's done at the receiver (obviously, the same Walsh functions are used). The interleaving's done to ensure that the probability of continous runs of corrupted bits are minimized (i.e., so that the error correction will actually work in the presence of correlated bit errors). Jamming AMPS, on the other hand, is trivial as it's merely a frequency modulated analog signal. -- end --