mobile (cell) phone jamming

Are you a chemist or pharmacist? Is it dangerous?

I thought the degradation byproduct are acetic and salicylic acid. Acetic can't be that bad and salicylic - well that's wart remover so might be, yet aspirin metabolizes in the body to salicylic acid.

Did find an interesting google on it . . .

aureus?associated

the major metabolite of aspirin, acts at the

fibrinogen, fibronectin, and ?-hemolysin ?

host tissues and, now, potential therapeutic

So aspirin may help in preventing staphylococcal infections. Handy to know if you're planning on a trip to the hospital.

Like they say: "Its not just for breakfast anymore."

-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----

-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

I read in sci.electronics.design that default wrote (in ) about 'mobile (cell) phone jamming', on Mon, 22 Dec 2003:

I studied chemistry for some years. Perhaps not dangerous, but unpleasant to take because it's a lot more acidic, and aspirin is so cheap that there seems no point in using outdated stuff.

I agree. The car lock remote uses infrared (I think) and transmits a very specific signal that the car receiver detects.

The jammer would use cellphone frequencies (around 9GHz and similar bands, I think) and would need to transmit--I think--white noise across the target band, strong enough to drown out the signal the phone is already receiving.

You're making it up at you go along !

No, how you jam a GSM phone is use a UHF mixer oscillator with a 45MHz Oscillator which is the difference between the RX and TX of a GSM phone, and put in a delay line so that the output of the jammer is in phase with the phones input, causing feedback that stops the phone working.

Allegedly similar mixer osc devices (without the need of a delay line) have been used to jam amateur radio, police, and PMR repeaters. So I've been told

Steve Terry

You'll have to run that one by me again - now I think *you're* making it up as you go! :-)

Ken

A GSM phone receives on around 950MHz and transmits 45MHz down on around 905MHz with a difference in multiplexed time slots, so if you can make a little receiver that takes the 905MHz signal from the phone and mixes it with a 45MHz osc putting a signal back out into the phones receiver, and time delayed so it interferes with the same time slots in the phones receiver you'll get a howl round, or you won't, as the phone would lose the network trying to do so

Steve Terry

phone

So how does the system know which frequency channel the mobile is on (there could be several mobiles operating on several different channels simultaneously) and how does this system cope with frequency hopping?

You mix 45MHz with the phones own TX signal, from any phone nearby. Then retransmitting itself up 45MHz into the phones receiver.

Whatever channel the phone is on, it's always a precise 45MHz diference

Without the phones transmit signal all the jammer puts out is it's 45MHz osc

What so difficult to understand ??

The difficult bit is adding the time delay so the phones TX time slots overlap it's own RX time slots, otherwise the phone simply won't hear itself, feedback, and stop working.

Steve Terry

the

phones

phones

network

(there

osc

overlap

But they randomize time-slots within the TDMA. For just one problem with this technique.

Ken

osc

overlap

Ah, I see, you mean a broadband jammer (otherwise it will not cope with two phones transmitting on different channels). For some reason I was assuming that it was some elaborate narrow band jamming device. Why not just transmit a burst of white noise at 950Mhz with a 45MHz BW?

diference

two

assuming

transmit

Probably not. Particularly a CDMA system, unless you put out so much power that you were obvious to the crowd - the car battery, being up against a wall, being cavity probed by the FBI........

Ken

I am no RF engineer, but IIRC, building a broadband transmitter intentionally is not that simple. Also the noise will have to be above the signal from the base station transmitter (say 50W transmitter?). I wonder if it would not be easier to jam the uplink signal as this would only require the jammer to transmit in the same order of power as the mobile.

If this is about North America you are way out to lunch. All we have here are RF remote controls for cars.

and transmits a

Broadband yes, but not broadband jamming, it's providing from the phone TX a mixed signal to go back into a phones RX, the more phones within it's range it's trying to mix, the weaker the individual output signal from it.

Steve Terry

Doesn't have to be precise, just as so there's enough time slots interfered with to stop the phone from working.

Steve Terry

A broad UHF input 45MHz mixer osc with broad UHF output is very simple to make

A broadband UHF white noise jammer would have to transmit very much more power to have an effect

The whole point of the phone operating on a 45MHz split with odd phased time slots is so the phones RX doesn't hear it's TX. Upset any part of that cycle with a relatively low signal, and the phone stops working.

Steve Terry

stops

So what sort of delay would be necessary and to what tolerance?

A few microsecs ? I would guess interfere with as little as 20% of the slots to stop the phone working

If there is already a random element in the slots maybe just letting the phones RX see it's TX with a nearby 45MHz mixer osc could be enough ?

Steve Terry

ROTFLMAO! Infrared ?:-) 9GHz ?:-)

The best defense we have against such folly is that the perps are village idiots ;-)

...Jim Thompson