cell phone jammer

"John Smith" wrote in news:TeLqe.5247$ snipped-for-privacy@news.sisna.com:

You're not going to make an oscillator with that wide an output signal. It still has to be band filtered to prevent interference with other frequencies used by emergency and other services,too.

The carrier levels are low enough that you can swamp them with white noise. (for a *short* range)

Easier,cheaper,SIMPLER;remember the KISS principle.

well,there's ~800 Mhz band,a 2.5 Ghz band,nad one other that I can't recall.You are not going to get a single VCO that would cover all CP bands;even military jammers use multiple signal sources.One single antenna would not even work for all the CP bands.

IIRC,most of the newer phones use 2.5 Ghz.

Interesting. After the Loma Prieta Earthquake (the one that interrupted the world series) in 1989, Landlines were almost universally down, and the only way people could talk was via cell phone.

I guess different disasters have different symptoms, so to speak.

--Mac

... this looks like it is on the right track...

John

Jim:

Actually, if the rf generated is wide enough, just use a diode noise generator as a signal source, with two or three bandpass filters, buffer and amp each band feeding it to its separate antenna... just might work... or, if most cell phones are on just one band--just filter for that band...

John

Yes I see that now (I reread the thread). Rich is just such a pacifist, eh?

Certainly not. I'm not for jamming them either. If you don't want them used in your theatre, simply make it like any other large building. Metal roofs and walls seem to turn my CP reception to trash in most buildings. ...not that I care much.

It differs. I'm not in line for any hurricanes, nor earthquakes (though the latter is has a higher probability). I just got fed up with the

Maybe if I lived in the swamp I'd feel differently. ;-)

keith wrote in news: snipped-for-privacy@att.bizzzz:

so,instead of economical short-range jamming,those business or property owners must engage in expensive re-building in order to block the CP signals? Why place such a costly burden on them? The very nature of cell- phones makes jamming only possible for short ranges,thus it would not be any widespread interference.

Seems to me that earthquakes might knock down CP towers,or cut electric power to them.Tornados or floods can also cut CP reception in affected areas,too.

I have a 1.5KW magnetron from a commercial microwave oven, hooked up to a sloppy waveguide which exhibits multiple resonances and ran out into space would probably have the effect of jamming most if not all cell phone freqs--I think the output is pretty dirty and running off of a unfiltered/unregulated supply the output should be all over the band and spanning tens if not hundreds of Mhz with the related harmonics...

John

Jim:

Yes, the waveguide/horn would have to point up at a cone, with the aperture spacing between horn and cone somewhere near the desired freqs to produce a roughly omni-directional signal...

John

Geesh!

I wasn't advocating building one, just was pointing out that the jamming is NOT difficult, or obtaining GREAT jamming power...

you would have to have a about a 300 ft extension cord on that thing anyway, I certainly would NOT want to be around it... LOL!

Honey, I microwaved the kids!!!!

Warmest regards, John

"John Smith" wrote in news:XXmre.50$ snipped-for-privacy@news.sisna.com:

Not all cellphones use the 2.5Ghz band. Also,without a decent antenna,you would radiate a directional signal. Note that CP towers use multiple antennas to get wide coverage.

And with that sort of transmission,I suspect you'd interfere with enough civil and military receivers that the FCC (or US military) would locate and come down upon you fairly quickly.

"Jim Yanik" wrote

I did a search and I found Cellphone jammers on the internet for sale to police and federal agencies.

As I recall, there is a high power one SWAT teams like to use since it jams several square miles and cuts commumication between people they are after and any possible outside people posed to help in escapes and such.

Lower power versions cover a single building, more or less, depending on what's in the walls and so on.

Of course, private citizens can not buy these things legally, but I imagine there are ways.

Jim

Hopefully you'd be the first (and only) one to look up and see if it was working.

Ken

Warmest many things... :-)

There were so many suggestions less than practical it was hard to figure out who was just taking the piss.

Cheers.

Ken

More important -- it kills the press coverage. The last think HRT et. al wants is the hostage talking to the press.

A good post...

A more efficient way is to use a narrow pulse for the modulation at a specified rep rate.

The rep rate is equal to the channel spacing.

The pulse width is such that the first sinx/x null is approx equal to width of the band to be suppressed.

The pulse is used to modulate a carrier on the channel frequency in the center of the band.

That way, all the little spikes lie exactly on the channel frequencies throughout the band, and the amplitude is high, since the pulse width has been chosen so that the amplitude is RELATIVELY constant throughout the band.

In this manner, the interference is positioned on the center of each of the band channels, and no energy is wasted filling up spectrum that does not contain signal.....

Even better if only the "supervisory" channels are jammed in this manner. The data channels don't really matter if the phone cannot receive supervisory instructions from the cell tower...

Furthermore, if the rep rate is dithered, it may be more effective , but that would depend on the characteristics of the receiving demodulator. Suffice it to say that white noise is VERY innefficent compared to a solid carrier which uses the characteristics of FM suppression.....

Just a suggestion from an old, retired, EW engineer.... (Electronic Warfare)

This ain't rocket science, but communications engineers are a lot more likely to come up with useful solutions since the cell phone specifications are not flexible, and cannot change things like frequency and modulation to deal with jamming..... but ya gotta really understand how the systems work before you can efficiently blank them out.... Andy

What I want is far harder; I want a universal cell phone ringer.

Once you walk past the "All cell phones off" sign at the theatre, your phone rings. So does the next guy's. You answer [holding up people] but no one is there. You hang up, but a minute later, it rings again.....and again.....

By the time the curtain rises, you've turned it off or your neighbors have beaten you senseless... and stomped it into junk.

WTF HRT?

Thanks, Rich

Hormone Replacement Therapy last time I checked !

Ppl should be more careful about 'bandying about' dumb acronyms.

Graham

Hostage Rescue Team; the Feebee's pseudo-SWAT team. And I left out the word "taker" -- I meant to say "hostage-taker" above.. As I recall, there was lots of griping at the Waco press pool as the FBI jammed The Branch Davidian's, and the press's, phones.