Instructables
Picture of How To Create Your Signal Jammer
For a long-long time many people were looking for this cool recipe of making something interesting for yourself. And I was one of them until last days. In my quest I came across the Jammer Store blog post called How To Make Your Cell Phone Jammer: DIY Guide. It inspired me to make something like that by myself.

All necessary info, schemes and pictures are there, so I tried. The result is represented in this humble guide for you.
 
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Step 1: The Basics

Picture of The Basics

This signal jammer uses 800MHz frequency to operate because many cell phones are working on the same frequency. So I chose the sweeping oscillator as my VCO. It is really efficient yet may be difficult to use if you are beginner without some semi-professional RF-testing tools.

The clock oscillator (45MHz) is driving a local oscillator port as my noise source and is located on the mixer of the mini circuit. To equate the impedance of a clock oscillator with the mixer there is an impedance matching network. Local oscillator signal goes through this network and impedance is matched.

The 800MHz antenna from the old cell phone is connected to the RF input (mixer port). The RF output then goes to the amplifier located on the mini circuit. The amplifier will increase produced output by 15-16dbm of pure power. The empowered signal is going to another old phone antenna.

Step 2: Your Jammer Works!

Picture of Your Jammer Works!
GSM800 cell phones have their frequencies separated by 45MHz exactly. So when any cell phone tries to make a call - it becomes blocked by itself! The phone talker will hear its own voice.

You can also keep in mind that this cell phone signal jammer can block all cell-based trackers which use your car GPS to track you down and record the data. Even IEDs are probably could be jammed, at least those ones controlled by cell signals.
shiaulteyr2 years ago
Swapping out the sweeping oscillator with one from the phone itself, an old router - if you're interested in those bands - and other electronics (such as old RC toys, which makes those crack-of-dawn RC plane enthusiasts quite down nicely) should work with this design too. That is, in theory at least. Great project to experiment with though!! Good work!

Just on the IED topic there - we used to use a similar device in Afghanistan when the opportunity presented itself and I know that many Police agencies have them in their arsenal - where they provide, I'm sure, much more use than they did for us! (By the time you find out it's a cellular triggered device, you're probably already picking up what's left of it after it went off the day before! Not to mention, setting the phone's alarm as a backup/failsafe is immune to jamming - as are grenades).
and i hate to say / type this. depending on the phone. the alarms wil still go off even if its in stand by mode. then depending on the phones battery, it can be in stand by for up to a week. if u want it to last longer put in a small solar panel.
BearGrills (author)  shiaulteyr2 years ago
Thank you for nice words and advices! It is pleasant to know that similar devices are saving lives out there :)
am tech1 month ago

but I think I'm going to make it anyway!

am tech1 month ago

isn't this illegal I was reading a jammer article that says if they caught you th

ed lock you up and throw away the key.

shubhamelec2 months ago

can i use a crystal oscillator insted of the one u used in the project

shubhamelec2 months ago

can i use a crystal oscillator insted of the one u used in the project

shubhamelec2 months ago

can i use a crystal oscillator insted of the one u used in the project

santpyara2 months ago

pls show the circuit

hohum4 months ago

I noticed there is knot of red and black, is that where you put the ferrite cores?

Shajeel7 months ago

mere baaaaaap circuite tou dikha de kam se kam

zarmons7 months ago

hi you there.can you send me a schematic diagram and the component part? my email zarmons_613@yahoo.com.i like you project and i want to make like this kind of project.

thanks adnvance

zarmons....

nicostar231 year ago
I want to make one that will crash everything in my school. What should the output(s) be?
if u go that route. u can be branded as a terrorist. because u never kno who might have a pace maker 4 thier heart.
badsting1 year ago
Where should I get old phone and which best MHz ?
try dx. com an or alibaba.com then try many pawn stores . uill sure to find 1 yr looking 4.
hiyer2 years ago
hey i want to make signal jammer as my project . so can you pls send me the list of compenents and the procedure to my email id i.e hvignesh91@yahoo.com
kcrow11 hiyer12 months ago
the list of components ins written clearly in the circuit diagram....open it and you will see! the procedure on building one of these is what the entire instructable is written about, read the article before asking questions.
bro if sm1 hs send u the list of ths component plz send me also
my email id iz saber.shafi@yahoo.in
bilaljarral2 years ago
helo bro
can you help me make a jammer if you want plz sent me all component and detail on my email bilaljarral302@gmail.com,
i hope u help me
if you cant figure it out from the circuit posted above, you have no business tinkering with such things...one could really hurt themselves from electrocution! all the components are listed in the circuit schematic and all the help you need is written in the instructable.
bro if sm1 hs send u the list of ths component plz send me also
my email id iz saber.shafi@yahoo.in
BearGrills (author)  bilaljarral2 years ago
There is no need to write few times, don't clog the comments please
rg
erotologue1 year ago
Hello BearGrills,
I planning to built this jammer but I would like to increase is range ( I'm not talking about the antenna ), how could I do ? does it need another amp ?
is there any modifications to be done to circuit diagram ? . My email id is slugha_432@hotmail.com
paddys0111 year ago
Wonderful project - can anyone tell me if this would allow FM radio signals to be received whilst blocking phone signal?
Hello Bear Grilles,
I am very interested in this project and In the picture of your model I found a transistor but I dont find any in the circuit diagram , is there any modifications to be done to circuit diagram . My email id is adithya.yuri@gmail.com
http://www.arrl.org/news/fcc-issues-two-forfeiture-notices-for-cell-phone-jamming
Hello Bear Grilles,
I made an account just to ask, can you end me super detailed instructions as well as what each component's function is, I have no idea what I am doing whatsoever, but would love a quick lesson on it. My email is EArmendariz000@gmail.com
soundman641 year ago
Hi BearGrills,
Interesting jammer idea that - getting the received frequency to generate a jamming signal 45MHz offset from it. In your experience, can you tell us how effective it has been in practice? The receive and transmit antennas are quite close. So, I was wondering if the strong transmitting antenna signal would overload the receiving signal and mess the whole thing up (even though they are 45MHz apart)?
Would you not need to filter the receive signal to keep the transmit signal away from it?
Also, it probably wont block one-way text messages being sent from those accursed GPS tracking thingies, will it?

Thanks.
dinodhayal1 year ago
hi sir/madam,
can you help me make a jammer if you want plz sent me all component and detail on my email skddinesh295@gmail.com,
i hope u help me
dinodhayal1 year ago
an you help me make a jammer if you want plz sent me all component and detail on my email skddinesh295@gmail.com,
i hope u help me
mammasboy1 year ago
this is an awesome idea, could you provide a parts list and a "how to" for the circuitry side of things? i'd love to make one of these
JFaust782 years ago
I am not a professional electronics guy, but could someone suggest a part number or link for the clock oscillator. I am finding many of them, but do not know which would work for sure. Thank you so much for the great post!
sumalyo2 years ago
very very very very gooooooooooooooooood
bilaljarral2 years ago
i want make a mobile jammer plz help me
BearGrills (author)  bilaljarral2 years ago
All details are here in this DIY, use it and make your jammer ;)
hi bro can you send me all component from your project to my email kukuhmoeslim@gmail.com thank you so much. i hope you can help me please....
BearGrills (author)  kukuhmoeslim2 years ago
Hi!

Sorry, but I can't remember all components now because it was long ago when I made my jammer. Just follow the instructions I wrote here and pick up similar components because you'll need to test their compatibility anyway.
fegundez13 years ago
as it has been widely known that most cowardly ied device users do use cell phones to trigger their devices it boggles the mind to think that the military doesn't use some kind of device like this to stop some of the carnage.
No doubt the US military has counter measures. most likely developed before other departments of the US government empowered terrorists the US was friendly with the the nut & bolts of IED. Frankly while I understand why the use of IED is characterized as cowardly, I don't agree with that assessment even though they are being us against US soldiers. Those employing the IED are are in their own country are friendly to that country, and are using them against an occupying force. The use of the IED is no more cowardly than a pilot dropping bomb from the safety of miles above or person sitting at a console in the us commanding a UAV to fire a missile. In the event the roles where reversed Americans would do the same to any army that dared to enter the US. IMO it's going to be the unhealthy narcissism of Americans that will be our ultimate down fall.
The jamming of radio signals by the US government and/or military is old news. No reason to think they are not doing so now.
JKR fegundez13 years ago
In both Afganistan and Iraq the coalition forces use a very complex jamming system that jams multiple frequencies. Look up JCCS-1 and the CREW system. The Army just brought back an MOS in Electronic Warfare from lessons learned in country. I spent a year in Iraq installing and maintaining CREW systems, cool stuff to work with most of it was classiified secret..
BearGrills (author)  fegundez13 years ago
Actually they do use very powerful and completely reliable jammers for disrupting IEDs. The post about it you can find at the Wired.com's Dangerroom, the Iraq invisible war or something like that.
static3 years ago
When I read microstrip line on the schematic, I had something else in mind, that I was seeing it on the most predominate photo of the completed board, I assume here microstrip line means the small coaxial cable.
pcooper2 static2 years ago
No, a microstrip is a strip of conductive material isolated from a circuit board ground plane by a layer of insulating material (dielectric). The characteristic impedance of a microstrip depends on the dielectric constant, the thickness of the insulator and the width of the conductor and is chosen to match the output impedance of the driver for optimum power transfer. In effect, a microstrip functions much like a coaxial cable.

Connections to microstrip transmission lines are usually made with surface-mount components, since a PCB feed-through hole would introduce an impedance discontinuity that would alter the characteristic impedance and cause ringing and unwanted electromagnetic radiation. The circuit board depicted in this project is constructed almost entirely using microstrip design techniques.
static pcooper22 years ago
Yes I understand what you mean how strip lines are use at the frequencies in construction, now you brought it up. I was unfamiliar with what was used on the schematic to depict the strip lines. For me anyway it was difficult to follow the photos of the populated board.
snackpakSam2 years ago
Hi BearGrills,
Interesting project! Different and simpler approach to other "bubble" jammer projects out there. I really want to independently verify that this works. I'm a EE, but no hi-freq/microwave background, so I'm having trouble understanding the microstrip requirement in your schematic. In your photos, it doesn't exactly look like it is a high precision build (no offense intended), but my understanding on the microstrip is based on some pretty precise calculations using the dielectric thickness, ground plane, and trace dimensions. That, in conjunction with the fact that the co-ax doesnt seem to be spec-ed either makes me wonder how you actually implemented this part of your schematic. Any chance you could shoot me some details? Is there a backside ground plane we're not seeing, why is the striped component on the right of the photo (assuming inductror) is not connected on one side, why the ferite bead? Any other implementation details would be appreciated too! email is classnotes998877(at)gmail.com
Thanks,
Sam
BearGrills (author)  snackpakSam2 years ago
I've sent you an e-mail ;)
pcooper22 years ago
Cell phone jammers are available as commercial equipment from several Israeli, British and Asian companies, although they aren't permitted for civilian use in the United States. The same thing could be achieved by enclosing the premises with a metal screen, without having to use active jamming, and it often occurs inadvertently in buildings that use lots of steel panels and steel-reinforced concrete in their construction.

The whole cell phone spectrum doesn't need to be jammed; only the frequencies used by the phone to establish the "handshake" with the cell repeater. If the phone can be fooled into thinking no repeater is available, a call can't be initiated or received. The phone will just display "No Service".
BearGrills (author)  pcooper22 years ago
Yep, but metal screening is used in specialized buildings, but not in every one or outside.
BearGrills (author)  pcooper22 years ago
Metal screens are used in special buildings but not everywhere. And it is also not used outdoors.
nasim862 years ago
hye bearGrills.. im really intrested on ur project.. im doing my FYP right now.. can u send me the detail bout this signal jammer project.. thank you
BearGrills (author)  nasim862 years ago
All details are here, but if you need more complex schematics, you can use those from the blog post I've mentioned at the beginning of this DIY.
nasim862 years ago
hye bear grills.. im intrested on ur project for my FYP. can u please email to me the complete steps for these signal jammer..tq
aashu0292 years ago
Greetings Bear Gills
i want to know that how can we increase the range of this jammer and if there is any room for that... Kindly send me the complete information regarding the necessary circuit elements used in this jammer and the basic connections. Kindly mail me at lone_aashu@yahoo.com
Eagerly waiting for your reply
rivetgeek3 years ago
it should probably be noted that this sort of device is totally illegal in the US
JuCo rivetgeek3 years ago
not true... hospitals use them instead of dealing with the jerks that think that they're call is way more important than someone's life and corporations use them for security. the biggest problem is that they usually don't set them up properly and the "bubble" will reach beyond their building's walls.

to be fair, you might have meant that it's completely illegal for just some random person to use one... in that case, yeah, you're right. and it's probably a HUGE fine if you're caught doing it.
rivetgeek JuCo3 years ago
The FCC would beg to difer:

http://transition.fcc.gov/eb/Public_Notices/DA-05-1776A1.html
And your point is. Like we care...
Most people with an IQ over 80 tend to dislike federal prison. Let me know how it works out for you though.
static JuCo3 years ago
When something doesn't make sense it's probably not true. In event the emissions of a cell phone could interfere with medical equipment it's highly unlikely the hospitals deliberately transmit on the same frequencies.
schkip1973 JuCo3 years ago
Do you have an example of a hospital that sends out radiation to interfere with a cellphone, while at the same time not interfering with medical equipment?
Also it's not a bubble.
Jam early, jam often.
seolfor3 years ago
There are situations in the U.S., such as teaching electronics, where the making of the device is not illegal. Of course, using the device is a whole different matter. Those who might have a need for it at home, might be better off turning a small room, or even just building a portable, faraday cage. http://en.wikipedia.org/wiki/Faraday_cage

Nice instructable, and thanks for demonstrating how to make one of these.
static seolfor3 years ago
To keep it short as possible. I can't think of anything that could be taught by building this circuit that couldn't be taught by building circuits that don't violate Federal regulation to construct or use. AFAIK the idea that educational purposes trump Federal and/or State legislation is unsupported myth.
seolfor static3 years ago
With all due respect, I guess we'll just have to agree to disagree. I've worked with law enforcement as well as with the broadcasting establishment, and I get the feeling you do or have.

The operation of transmitters designed to jam or block wireless communications is a violation of the Communications Act of 1934, as amended ("Act"). See 47 U.S.C. Sections 301, 302a, 333. The Act prohibits any person from willfully or maliciously interfering with the radio communications of any station licensed or authorized under the Act or operated by the U.S. government. 47 U.S.C. Section 333. The manufacture, importation, sale or offer for sale, including advertising, of devices designed to block or jam wireless transmissions is prohibited.

Cell phone blocking devices are used by federal officials under certain circumstances. Privacy rights of property owners may affect the policy and application of law within buildings. The FCC may issue a permit that waives the law for private use.

Nowhere does it state that making them as proof of concept or for teaching is illegal. Most technical schools that each do take the time to get the FCC waiver just to be safe. And, also as stated, privacy rights of property owners (this includes private citizens) may affect the policy and application of the law within buildings.

As most of theses devices can be built to limit the range, using it in one's own household may fall under the private rights of property owners as long as it does not extend beyond the building and affect the public in general.

It's the same with explosives. You can make them in a teaching environment, say for a chemistry class, under controlled conditions. But the majority of explosives are illegal to make or use by the general public.

Knowledge is not dangerous. It is how that knowledge is used and applied that can make it dangerous.
Always a "killjoy" in there.
BearGrills (author)  seolfor3 years ago
Totally agree! If someone afraid of being charged for illegal public use, make this one for yourself, for home usage, with small jamming radius enough to cover the area but not interfere with outside, and everyone would be happy :)
JKPieGuy2 years ago
Hey I have a quick Question, how far does the signal range? If you could answer my question that would be great. (If it's under 10 feet that would be great also.)
BearGrills (author)  JKPieGuy2 years ago
I can't tell you the exact jamming range because it depends on the phone you are trying to jam, but it is small. This signal jammer is not powerful enough to create huge jamming power thus I doubt that signal range would be more than 10 feet.
Ok, cool thanks. I just wanted to use the jammer on these annoying kids in school who are always texting during class and tests. I also have another question, is it possible to add an LED to the project as like an indicator light?
BearGrills (author)  JKPieGuy2 years ago
Yes, of course! You can use LED indicator to see when the power of your jammer is on, for example.
Awesome. Would I have to wire it differently or add some thing so that the LED wouldn't interfere with the project or can I just connect it directly to the "on" switch?
BearGrills (author)  JKPieGuy2 years ago
I guess it would be simpler to connect your LED directly to the switch, and they would use the same power source.
Thanks. I was thinking that, but I wanted to make sure because I know that if you use an LED with a project that uses sound it affects how things sound.
BearGrills (author)  JKPieGuy2 years ago
You are welcome! ;)
Hey I'd hate to be a pain but do you think you could make a list of exactly what parts and how many of each you need to make this project. If you could do that it would make it allot easier to order the parts. Thanks. :)
BearGrills (author)  JKPieGuy2 years ago
Sorry, but I have no time right now to do the list because I am busy with many other stuff now. But all necessary components are described here so you need to find similar ones and just match them together :)
Well I appreciate you responding to my comment and thanks I understand.
I mean I know what most of the parts are and would I be able to find the exact parts of some of the other stuff like at Radio Shack?
BearGrills (author)  JKPieGuy2 years ago
Yep, I guess you would find all you need there.
sanagol2 years ago
iv got a better jammer than yours that can (jam)for up to 50 ft but its illegal ang destructif its called an EMP generator if shuts down everything electronic for a 5hours - for ever!!
BearGrills (author)  sanagol2 years ago
Yep, you've got EMP generator but not the jammer, they have different principles of operation. For example, you can't use your device in a bus because it will stop with all its electronics being shut down :)
Always a "killjoy" in there.
Higsby2 years ago
Greetings, BearGrills!

My group and I are currently making this Signal jammer for our Communication Electronics class. We have a few questions, if it would be alright for you to answer:
1) For the inductor between the two 22pF capacitors, is it a handmade coil? If so, how many coils did you make and what materials? If not, what kind of inductor did you use? Because we're not seeing any inductor in your photos
2)Why use a microstrip line? Is there a difference from just using an etched surface on the pcb?
3) And we were wondering if you could email me a few more details about the jammer. [Joarjdlc@gmail.com]

Please and Thank you! We look forward to your response!
BearGrills (author)  Higsby2 years ago
I have sent the reply to your e-mail.
if it does what I think it does, it would be perfect for the movie theatres in Montreal.
BearGrills (author)  jsyracopoulos3 years ago
Yep, it is great for using in movie theaters, and when you'll make it, you'll enjoy it ;)
preethesh_k3 years ago
i'm planning to make this as my final year project.. please give guidelines.

preeshenoy@gmail.com
BearGrills (author) 3 years ago
Yeah, it is great for using at home for personal safety and not to harm others. However it is very tempting to use it to silence some annoying cell phone blabbers :)
Though it is illegal to do that, thus you need to think twice before doing so.
kelseymh3 years ago
http://en.wikipedia.org/wiki/Mobile_phone_jammer#Legalities