cell (mobile) phone scrambler jammer

Can anyone offer some tips on building a cell phone jammer. There are
apparently no laws about this (yet) in the country where it will be
used. Purpose is to interupt/disable these devices during doctoral
thesis dissertations in a typical lecture hall. Ideally an incoming
signal would not be detected by the phone, so no ring signal, and also
there should be no way to ring out. I can build simple circuits if
someone can point the way. I am currently a bit hesitant to dish out
hundreds of dollars each for the commercial products and am thinking
that this might actually be not much more than a simple radio
broadcasting a loud dirty signal (something I could build very
cheaply).

Dominic

 

Station guards at the doors, and tell the lecturees to turn their phones
off. Or confiscate them, and give them back after the lecture.

Good Luck!
Rich

 

The mobile phone has been around for a long time now and these
low-tech solutions based on audience honesty have never worked.
We post signs, we remind people several times before and during
the defense and the problem persists. Quite frankly, there are a
lot of very rude inconsiderate people in academia who think their
mobile phone calls are so important that these rules do not apply
to them. I have proposed fines, which are being considered, but
are not likely to stop this problem. I have read that some Mexican
churches now have these jammers and they are working great. No one
can receive calls or call out and the system seems to stop pretty
much all attempted connections, which is what I want.

Since this is an electronics newsgroup, I am very interested in the
electronics solutions. This industry gave rise to the mobile phone,
and I think the jammers it gave rise to seem to be a very efficient
surefire accessory. So, has anyone here built a jammer?

Dominic

 

"Dominic-Luc Webb"

** You are asking folk to get involved with breaking the law if they supply
such info in a public forum.

** Irrelevant - see above.

** YOU have no way at all of building a successful cell phone jammer.

Commercial offerings are FAR more technically sophisticated than you naively
imagine.




.......... Phil

 

I am not asking anyone to break any law. I am asking for legally
accessible information for legitimate construction and use of these
devices that are otherwise sold commercially and used quite legally.
I recognize that in some locations there are laws restricting these
devices, just as there are places where telephones and phone books
are illegal, but this does not apply to the entire universe. If you
live under such a fascist regime, do not take part in this thread.
I definitely do not want anyone to get tossed into a trash can and
burned alive on my account.

As for others, thanks for contacting me offlist. I look forward to
more ideas.


Dominic

 

"Dominic-Luc Webb"

** Yes you are - fuckhead.

** That cannot be done legitimately on a PUBLIC FORUM !!!!!!!!!!

** You are a raving NUT CASE !!!

** You are a raving NUT CASE !!!

* I got a few suggestions for where you can go and what you can have done
to you.

IDIOT.




.......... Phil

 

So eject them !

Graham

 

RF screening of the hall will do this. I beleive that this method is now
being commercially adopted in some places.

Graham

 

Thanks Graham for this tip. Investigating jamming elsewhere I see
that one important consideration is that whatever mechanism is
installed cannot interefere with the complex electronics found in
modern lecture halls. This seems to be the situation at my instituion.
Aside from the more well general annoyance, at least some mobile phones
interrupt some of the audio-visual systems, effectively stopping
the speaker dead in his tracks. In fact, it seems that some phones
manage this task even without being connected to another phone, in
which case the batteries have to be removed. Rather irritating for
a large lecture hall to wait for one person to remove batteries due
to interference, then a few minutes later wait for another person
with another phone that interferes with another piece of equipment.
So it seems, the plot thickens, and the solution will be quite more
complicated.

I will look into the RF screening. Thanks bunches!

Dominic

 

Dominic, I think screening is your best option. Plus, it is not
illegal, at least not anywhere I can think. Basically you construct a
Faraday cage around the area you want to protect, so that any RF
transmissions are absorbed and grounded out so that cell phones,
radios, or any other device that use RF frequencies cannot be used.

Unfortunately, most of the people here in the forum live in the United
States, and as my interpretation of the law reads, it is illegal for a
private citizen to operate a jamming device(although the military uses
them, of course). That is why many people will not be able to provide
you with your requested information, as doing so would probably break
the law relevant to our country, even if it is not illegal in your
country. Sorry, but that's how things work.

Like I said, though, building a Faraday cage would probably be the
simplest solution. It requires no power, and protects ALL radio
transmissions, not just cell phone freqs. Plus it has the excellant
benefit of not being illegal, and as I am told, is being used by many
fancy resteurants here in the US to protect against noisy and obnoxious
cellphone users.

As for the actual construction, I've heard that using a ferrite coating
on plywood has enough strength to absorb the signals without building a
potentially more complex Faraday cage. I believe the magazine Popular
Mechanics has an article about the subject a couple months ago.

Anyway, hope that helps, and hope you can safely and legally accomplish
your goals without anyone getting into trouble. Cheers!

-J

 

"Juno"

** Cage a whole lecture theatre ??

That idea is very expensive and full of problems.


If the OP lives where using jammers is legal - then he knows what to do.

Buy one.




.......... Phil

 

This is my understanding. It is interesting that the sources
for me to buy the jamming devices are all in the USA. I get
the idea they are either not illegal to own or the government
is not actively pursuing abusers. I do not understand how the
information about how they work or how to build them would be
made illegal, but apparently this is the case. Historically,
such regulatory endeavors have been dismal failures. If someone
knows specifically where these laws can be found in black and
white (FCC???) that would be helpful since there are a lot of
liberal re-interpretations of laws amongst laypeople. I am not
familiar with American laws, but can guess this is governed at
the federal level.

The RF screen sounds like basic physics. Just a matter of knowing
what materials give most cost effective screening. It might even
protect audio visual equipment inside a lecture hall from ambient
mobile phone noise. Quite interesting.

Well, if so, this certainly sounds pretty cheap and plywood has been
used for walls. I will do some looking around. Giving the simplicity
and demand for such things in such environments, maybe there is
already a commercial source of building material.

Absolutely, Juno!

Regards,

Dominic

 

Or just give the ushers long sticks....

;-)
Rich

 

OK, please post a link to one of these devices, and we'll see what we
can do.

And if there _is_ such a thing available legally in the US, and you
don't have the wherewithal to control the children, then just buy one
and let the children run wild while you jam their phones. Sheesh!

Good Luck!
Rich

 

Jamming involves operating a radio transmitter. There is no other way.

In most (if not all) countries, subject to some exceptions for
(very) low-power, approved devices, it is illegal to operate a radio
transmitter without a license.

I am not personally aware of any country in the world that allows
unlicensed operation of a transmitter. Some have *very* dire penalties.

Apply for a license for the equipment you wish to use, in the jurisdiction
where you wish to use it, and see what happens.

 

The OP is not in the US, and this is not a US-specific NG.

 

http://www.worldgadget.com/pro­ducts.aspx?catID=326

http://www.phonejammer.com/ind­ex..htm

http://www.antennasystems.com/­cellphonejammer.htm

http://www.globalgadgetuk.com/­cell phone jammers.htm


http://electronics.howstuffwor­ks.com/cell-phone-jammer.htm


http://gbppr.dyndns.org/PROJ/m­il/celljam/

http://www.spymodex.com/index.­htm

http://www.phonebashing.com/

http://lists.jammed.com/ISN/19­98/08/0128.html

http://www.netline.co.il/LP.ht­m

http://www.cellphone.phoneacme­.com/cellphonejammers.html


http://www.networkworld.com/we­blogs/layer8/007857.html


http://www.cellularowl.com/cel­l-phone-jammers/cell-phone-jam­mers.html


http://mattplln.chaosnet.org/j­ammers/

http://www.zhangx.com/cellphon­ejammer.htm

http://www.happy.org.uk/cell-p­hone-jammer.html





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ferrite coating sounds like that paramagnetic paint (magnets stick to it)
I've no idea what that stuff costs but I feel the bill to paint the walls
and ceiling of a lecture theatre (and then re-paint in attractive colours)
could be thousands of dollars.

it migt be cheaper to put a microwave oven on the bench up the front
and cook any phone you see being used.

Bye.
Jasen

 

I do not claim to know US laws. I know that I had no problem finding
them, so you can do the same. It seems by some accounts that it is
illegal to give information about these devices, so I had better not
do this. Given that they are so easy to find, I only postulate that
the laws are not vigorously enforced or that it is not illegal to
actually own them. This is why I inquired about the specifics of the
relevant laws.


Dominic

 

Yeah, loads of us (not me personally, of course) have built them. But
no one with an ounce of sense is going to admit to it. They're
particularly useful in railway carriages, BTW. ;-)