From: nazif gündüç

To: PICLIST@MITVMA.MIT.EDU

Sent: 22 June 1999 22:55

Subject: Re: SV: gsm phone finder

Dear Robert,

 

    I have checked the gsm phone by spectrum analizer and at the normal position

it never sends any power output but when you speak or when it changes his cell operator then it gives 900 Mhz to 935 Mhz output power at this point it is very easy

to find there is a Gsm phone  but at the normal position it just receiving some thing

from cell center and never answer it.

    My problem is I need some code or ( like test signal or some data bus to make the Gsm phone say yes I am here ) other vise it just sleeps and never gives output

power.

 

    Best Regards

Nazif Gunduc

 

 

-----Original Message-----
From: Robert <robert.mellgren@VALHALLA.ORNSKOLDSVIK.COM>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: 22 Haziran 1999 Salı 23:35
Subject: SV: gsm phone finder

Well my guess and this is a guess or basicly an idea. Since i have very little experience in this. I do not know any good websites on this matter but i will try to help you with this.

GSM phones in Sweden transmitt in 900Mhz.

So make an reciever that reads 900Mhz for any kind of transmitting, and make some sort of circuit that triggers an alarm if the level of the input signal is high enougt. A GSM phone updates once in a while, exactly how far apart this happends i dunno, but nevertheless it updates by transmitting a burst of data, i guess it is some kind of " hey mama u got something for me? " then recieves what " mama " has got, then re transmitt it to verify that it was recieved correctly. This may be something yoy may be able to use. Since this happen on a regular basis. And if a person is talking on the phone well then you have that disturbance.

A a GSM phone creates a great deal of magnetic disturbance so to detect this shouldnt be much of a problem. i remember making a " active cable finder " in High school that basicly was triggered by a high enough magnetic disturbance. and lit a LED.

This was acomplished by making a wide coil of wire, which gathered the disturbance field and gave us a voltage in the coil., which we connected to a transistor that triggered at a certain voltage level. this is basicly a reciever. As far as i can tell a simple thing as that should work just fine.

But if what you are looking for is to make it impossible for a person carrying a GSM to get near this alarm i dont know, how do one detect a GSM while it is not transmitting a call or the mama beg. Hope someone elsa can help you with that, i also hope this helped somewhat.

 

Robert

 

P.S pardon my bad english