cellular phone jammer/jammer detector
Whelzorn
Posts: 256
Ok, before anyone starts screaming at me because jammers are illigal, first let me explain what my situation is here. I take a bus between home and school every day. I use my cell phone for various reasons, mainly checking weather/talking to family friends etc. Now, I am a pretty quiet cell phone talker, but some of the others on the bus are not. I am not necessarily bothered by this, but somebody is, and they have a cell jammer. I have plenty of reasons why it's not a dead spot, and can pretty much justify that it's not. So what I want to do is build a jammer for myself, basically to see if it really jams my cell. If so, I want to design and build MY OWN jammer detector based on the jammer. So I started trying to figure out how these jammers work, and finally decided that I have a vague idea that (based on pictures) it has an antenna that picks up cell signals, and replicates them with more power than the original, as well as smoothing them out, making the only detectable signal a bunch of gibberish.
The reason I'm not using a schematic from the interweb is because I wanted to try to make this thing microcontroller controlled. I have three microcontrollers at my expense: BS2, PIC16F84A (4mhz) , and an OOPIC2. Would anyone have any ideas/suggestions on getting me started on this venture?
(btw, I live in a VERY rural area, so the signal from the jammer would not affect anyone, because it simply could not reach far enough)
Thanks alot,
Justin
The reason I'm not using a schematic from the interweb is because I wanted to try to make this thing microcontroller controlled. I have three microcontrollers at my expense: BS2, PIC16F84A (4mhz) , and an OOPIC2. Would anyone have any ideas/suggestions on getting me started on this venture?
(btw, I live in a VERY rural area, so the signal from the jammer would not affect anyone, because it simply could not reach far enough)
Thanks alot,
Justin
Comments
This is a companys' forum...not a public domain forum...so it's moderated and any law enforcement official could easily follow back to them to find out that the company (in it's moderated forum) allowed such a thing to be posted.
Remember that a cell jammer would also jam someone from dialing 911 in an emergency! That's a big no-no!!
All you really need to do is get an antenna with an S meter readout (signal) and aim it around for the constant source. I doubt he's 'listening' for cells to turn on....the person just leaves it on and blanks the area.
They Iraqi gov't supposedly did this to through missile guidances off....but, it only worked for a short range....and what's the old saying, "Close counts in horseshoes and hand grenades....." But the bombs were close enough by the time the guidance was jammed...anyhow..ramble ramble
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Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
thanks,
Justin
[noparse][[/noparse]edit] yeah, I guess you were right, it's too dangerous to have something like that in the forum. (referring the missing post up top) well, I dont want trouble, so it's just as well. [noparse][[/noparse]/edit]
Post Edited (Whelzorn) : 4/12/2005 1:53:13 AM GMT
·· I cannot help you on the Jammer for many reasons.· But the hobbyist inside me tells me to at least tell you how to go about detecting the Jammer.· Cel-Phones operate at a given range of frequencies, which I am not providing·(You can find these out with little effort)...most jammers (Generalizing here) emit wideband noise in the frequency range of the device (Often at higher power, which is illegal).
·· All you really need to do is build a wide-band (Based around the Cel Freqs) RF detector.· The same technology is used in Bug detectors.· All they are is a high-gain VCO receiver/amplifier.· When the antenna gets near any RF source, the speaker starts squawking, or a meter goes up, or and LED lights, etc.· You would need to build an adjustment for sensitivity.
·· There!· Now no need to waste your time building a jammer and getting in trouble with the FCC!·
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Chris Savage
Parallax Tech Support
csavage@parallax.com
Thanks for the help!
Ham radio guys certainly have made some simple detectors with an antenna and a coil/cap combo. It's crude and doesn't give any indication of actual measurement...but you'll still get a relative measurement to the other signals in the area.
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Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
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Chris Savage
Parallax Tech Support
csavage@parallax.com
Rick
Nate
I work for the Canadian weather service and we had to install radars across the country. We would do these "town hall" meetings and there are a lot of ppl concerned because of radiation hazards and cancer.
They would hear the word radiation and freak out...but it's not THAT kind of radiation...the engineer giving the talk would ask, "how many of you have a cell phone.."
"how many spend more than 10minutes on the cell at a given time"...
Apparently, on the old cells, the exposure was much higher than our radar. Sorta put it in perspective. This engineer would refuse to use a cell phone....only when the digital ones came out, did he use one...and that was with a headset, so he didn't have it near his eyes.
Whelzorn, if you want to find out for sure if there's a jammer on board....watch your cell signal as you approach the bus (or it approaches you). Some buses are fairly decent on shielding....especially the old 'tin' buses. And some window tinting has lead in it which also makes it difficult.
The reminds me of a building near an airport radar....they were so worried about exposure that they had the building lead lined!! $$
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Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
·· They also run on a different set of frequencies.· The OP will have to learn about current frequencies and power levels.· I think the example of just using a Cel Phone as a source is a pretty safe way to test the jammer, since the theory applies the same.· It is a source of RF in that band.
·· I was impressed with your explanation of the "radar vs cel phone" issue discussion.· I think the lead-lined building went a little too far though.· Wouldn't lead poisoning be just as much of a concern as radiation?
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Chris Savage
Parallax Tech Support
csavage@parallax.com
Besides...you shouldn't lick walls!!
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Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
Interesting topic. My understanding of cell phone and jammers is the best method of jamming is to assign a bogus antenna location to all local phones. This does not require much RF power. It does require lots of knowledge and software. If the cell is being jammed by broadband RF the device would be large and noisy. To overcome an RF signal enough to break capture in the cell receiver requires a relatively large signal be generated. Depending on the field strength of the original signal, you must have at least 20 to 80 percent more signal strength from the jammer.
If you are generating a broadband signal your amplifier must be able to handle the bandwidth. At the frequencies of different cell
phones this would be quite a feat. I'm guessing 300 mW ERP might be effective. At this power battery drain would be significant. A good scanner would pick up an harmonic or perhaps a local oscillator frequency depending on how the individual generates the desired band of frequencies to be jammed.
Do you happen to know the frequency of the phone you are using? And the again the radiation issue pops up. maybe lead lined undies would help.
Sofa
I don't know if it's the distance of the contacts that would be the frequency select...or if you had to pulse the plug near the freq of the phones........nevertheless....who's gonna conceal a generator!!
"Excuse me...is that a magneto in your pocket or are you...blah blah!" haha
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Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
Sounds like a winner.
Sofa
Edit> Good one Steve!
If it's GSM, then it operates at 1900MHz in the USA(900 and 1800 in the rest of the world)
If it's not GSM, it may operate at 1800MHz.
About the old analogs also mentioned...
Here in Europe we had NMT450 and NMT900 (and a few others, but these two were the ones that worked)
They operated at 450 and 900MHz, and could have several Watts output effect, particularly the NMT450 phones.
The NMT450 system was the oldest, but it also had the greatest range, and when it was finally shut down a year or two ago, there were still more than 10.000 subscribers on it here in Norway.
The NMT systems(Nordic Mobile Telephone, incidentally) was used as the model when the GSM standard was developed, and several features was ported directly: Roaming(allowing you to use your phone and number in a forreign network transparently) and brand independence(The consumer could buy any brand of phone he wanted and it would work with whatever the network provider had. The provider could also shop around, buying bases from one company, transmitter antennas from another, and the rest of the infrastructure from a third)
Gotta stop now, before I go completely off the wall...
Now I realize that there are many good reasons for being so, but I teach and find that cell phones in a classroom setting are quite inappropriate.
My neice was enrolled in an inner city high school and teachers are unable to impound cellular phones.· As a result, half the students sit in the front of the class and listen to the lesson, while the others sit in the back and chat on their cell phones.
It seems to me that a jammer system for educational institutions should be allowed.· Especially when you are giving exams.
Reguard being jammed on a school bus, it could just be a bad ignition coil that is generating broad band RFI.· With the digital phones being so sensitive, I imagine that would likely play havoc with calls.
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G. Herzog in Taiwan
Kramer,
·· According to a news article I saw they are being used in some schools in other countries.· I couldn't find the exact article again, but I found this one as an example:
http://www.textually.org/textually/archives/004225.htm
·· Apparently France plans on jamming Cel-Phones in theaters and movie houses, but tweaking the technology to allow emergency calls (I don't know how they will do that).
http://www.nwfusion.com/weblogs/layer8/006483.html
·· And finally, here's a sad article which may add some weight to the concern of the OP.· Apparently some people are using them on buses because they don't want people talking during their bus ride.
http://www.nwfusion.com/weblogs/layer8/007857.html
·· And possibly in other classrooms...Note that this article points out that, not only are jammers illegal here, but if caught using them you could face very stiff penalties.· Food for thought...
http://daily.stanford.edu/tempo?page=content&id=14933&repository=0001_article
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Chris Savage
Parallax Tech Support
csavage@parallax.com
Yes, the US military is pigheaded enough for that...
(It was one of their generals who refused to have minesweeping tanks or amphibious tanks as part of the American task force on the D-day landing. It was another of them who refused to have the Sherman upgraded with a British long-barreled cannon, and instead waited until the American gun was ready. How many tanks and lives were lost? )
Another reason not to deploy such jammers is that if they're not in a warzone(where jamming the local networks would be OK anyway) is that they would need an explicit permission from the local government before deploying them.
(In the very fine print, deploying such jammers could be seen as an act of aggression.)
Don't get me started.
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G. Herzog in Taiwan
Post Edited (Paul Baker) : 4/17/2005 6:11:46 PM GMT
I don't see how the theatre could selectively block phones....unless of course, there are dedicated 'channels' used for emergency calls.
BUT, what if a relative had an accident and the family is trying to get the hold of you?! Certainly calling 911 is more important than receiving a call that little Timmy broke his toe....but it all depends on who you talk to.
Put in metal detectors and have ppl set their "comm. devices" to vibrate! Etiquette....
There are "radar gun" jammers too....the cops really hate those ppl that use them. But I'd hate to see the court case on this....
Say your on a bus and the bus gets in an accident. You had a jammer running to stop from having to listen to ppl talk about nothing (Seinfeld!). You're knocked unconscious and for 200ft around you, nobody can use their cells to call for help (I don't know the actual coverage). I'd hate to see what happens to the guy with the jammer if someone dies from lack of emergency services.
Sure...it's the What-If game....but really, sometimes asking a "loud talker" to respect the ppl around them works....otherwise, embarass them in front of the bus!! haha
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Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
"What-if" I decide to change careers and start robbing banks. In my plans for the big job I cut the landlines to the bank and carry a jammer in a briefcase to the bank. I bought myself a little more time to heist the loot·cause none of them dames can call the coppers from their cell phones.
Then again, if robbing banks is illegal, what would stop me from using the jammer other than availability.·I should stop while I'm ahead.
Sofa
Same goes for someone walking around at night with "certain tools" on their person!
Jamming of any sort is considered malicious behaviour as well. Ham'ers run in to guys running excessive power and transmitting over other ppl.
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Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
Let me take you back.
When you were in a theater and an emergency happened your people called the theater and they came and got you! But it had better damn sure be an emergency! Folks knew they were going to be out of touch and made arrangements.
When you were in school and an emergency happened they called the front office and let you know about it! But it had better damn sure be an emergency! There is NO excuse for having a cell phone in a classroom. You CAN be contacted in an emergency. Your rights are being trampled? How about the rights of the other students? (Can you tell I am a teacher?)
Maybe cell phones need to be reengineered so that a theater or classroom or other off limits area can be equiped with a licensed low power blocker transmitter that sends a special emergency only signal for a short distance. The phone will then only respond to calls from a 911 NOC. If your house is on fire or you child is in the emeregency room 911 will be called anyway. They can then call your cell regardless of whether you are in a no call zone. License fees can be charged to the operators of the blocker transmitters that will help fund the additional 911 NOC load. And the system could be set up to authenticate the blocker transmitters so that only licensed blockers will work.
This won't be implemented is because:
The cell phone companies want ABSOLUTELY NOTHING that will stand between you and your use of those cell minutes.
It would take a complete reengineering and relacement of the cell system.
It would take legislation to implement.
i think i will get one myself too. [noparse]:)[/noparse])
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5771290924
While I REALLY hate people talking loudly into the phone in public places, jamming such an important service is a very serious business and can land you into all kinds of trouble.
Pay special attention to the small print in that ad:
It is the responsibility of the customer to ensure that they have the legal right to import these products before purchasing from us. Upon purchasing, the customer becomes wholly liable for any legal issues that may occur as a result of the importation and/or use of these products in the destination country.
Note that it may even be intercepted by local Customs, and that WILL land you in trouble.
I agree that cell phones can be a bit of a irritation (I especially hate those idiots who leave their phones on and then answer them in the middle of a movie) but if one doesn't like cell phone use in public where it's generally tolerated, one should simply stay away from those places. I don't smoke, hence I stay out of smoky bars and restaurants ... we all have a choice.
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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA
He had one of those 'diver's whistles' in his pocket while he was at the cinema.
A moron had his phone on, responded when it rang(awful tune of course) and started yapping.
My friend took out the whistle, walked over to the moron and bent forward, then blew his whistle as hard as he could, straight into his ear.
Everyone in the room applauded when he walked back to his seat...
Now THAT's how to jam a cell-phone...
modern society survived just fine without cell phones until 2001. its a wonder in its self... *cell phone rings (seriously)* ... that we have become so dependent on cell phones in such a short time. i think cellular usage is a privilage, not a right and its every movie go'ers right to silence that is being trampled!
end devil's advocate
we all know that jammers are illegal so dont screw around with them are you could put an eye out.
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" Hey! Why is there silicone on my hemostats?"