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.

Step 1 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.

Comments

[shiaulteyr]

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).

[BearGrills]

Thank you for nice words and advices! It is pleasant to know that similar devices are saving lives out there :)

[kukuhmoeslim]

hi bro can you send me all component from your project to my email [e-mail] thank you so much. i hope you can help me please....

[BearGrills]

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.

[fegundez1]

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.

[static]

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.

[static]

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]

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]

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.

[static]

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]

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]

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.

[snackpakSam]

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]

I've sent you an e-mail ;)

[pcooper2]

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]

Yep, but metal screening is used in specialized buildings, but not in every one or outside.

[BearGrills]

Metal screens are used in special buildings but not everywhere. And it is also not used outdoors.

[nasim86]

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]

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.

[nasim86]

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

[aashu029]

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 [e-mail]
Eagerly waiting for your reply

[James Hauser]

Jam early, jam often.

[seolfor]

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]

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]

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.

[James Hauser]

Always a "killjoy" in there.

[BearGrills]

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 :)

[JKPieGuy]

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]

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.

[JKPieGuy]

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]

Yes, of course! You can use LED indicator to see when the power of your jammer is on, for example.

[JKPieGuy]

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]

I guess it would be simpler to connect your LED directly to the switch, and they would use the same power source.

[JKPieGuy]

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]

You are welcome! ;)

[JKPieGuy]

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]

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 :)

[JKPieGuy]

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]

Yep, I guess you would find all you need there.

[sanagol]

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!!