Radio Frequency

Cell Phone Detector

This is a mobile phone sniffer circuit that can detect the signals being used in the GSM (Global System for Mobile Communication) band at about 900 MHz. Since the signals are digitally encoded, it can detect only the signal activity, not the speech or the message contents. A headphone is used to hear the detected signals.

The circuit schematic is given in the .rar archive attachment. There are two separate detector units. Every detector unit consists of a dipole antenna, a choke and a diode. The antenna receives the GSM signals in media. Then a small amount of charge is induced in the choke. The diode demodulates the signal and finishes detecting. The diodes must be schottky diodes or germanium diodes. Since the forward voltage of a silisium diode is high, it won't give a sufficient result in this circuit.

LM358 amplifies the received signal. It contains two separate op-amps that are supplied by a common power source. R3 and R7 resistors determine the gain of the amplifiers. When the resistor values are greater than 10M then the noise level increases. If they are small like about 100k, this time it becomes harder to hear the signal.

Click here to download the schematic and the PCB layouts.

Component List

R1, R5 : 100K 1/4W Resistor
R2, R6 : 1k 1/4W Resistor
R3, R7 : 8.2M 1/4W Resistor
R4, R8 : 220 Ohm 1/4W Resistor
R9 : 2.2K 1/4W Resistor
D1, D2 : BAT43 Schottky Diode
C1, C2, C4 : 100nF Polyester Capacitor
C3 : 100uF 16V Electrolytic Capacitor
L1, L2 : See Text
U1 : LM358
J1 : 8 Pin Socket
J2 : Stereo JAck
1 x 9V Battery
1 x 9V Battery Socket
1 x LED
1 x On/Off Switch

The diodes, gain of the amplifiers and the length of the antenna is critical in this circuit. Calculating the length of the antenna is simple. The formulation is given below.

λ=c/f = (300.000km/h)/900MHz =33.3 cm Then; Antenna Length = λ / 2 = 16.6 cm

So there are four pieces of antenna and each one is about 8.3 cm long. The wire type is not critical but its better to choose a fairly thick wire that will not bend too easily. It is a 1.5 mm diameter wire seen in the photo that we used. The two antennas must be positioned perpendicularly.

The chokes are 10 turn molded chokes. The wire diameter should be about 0.5 - 06 mm and wound around a 5 mm cylindrical object.

Diodes are very critical. You should use one of BAT43, BAT45, AA112, AA116 or AA119. When a silisium diode is used the circuit also works but the detecting area becomes very very narrow.

Y.Erol

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Comments (34)

Stainless

Would it be possible to use this to triangulate a signal? Could you use it to figure out who's texting in your class or something like that?

siddharth

can you suggest any other antenna for this project ?

parveen kumar

how can take results from this circuit and can we hear that particular detected signal by this circuit at the same time

Donny

Is there a possibility to get a more detailed discription on the circuitry operation to my email?

Gurumoorthy

sir,
i'm in a need of mobile circuit diagram for my project... so, can you please send some sites to find those circuits... especially nokia circuits....
Thanking you....
K.Gurumoorthy

Jahid

Sir,
cell phone detector can cover only 1meter .Please can u suggest me how i can increase the covering area.I will be thankful if u please give me the suggestion.

john

Hi jahid did you use a schottky diode or any other popular ordinary one?

Ramesh

Sir,
cell phone detector can cover only 1meter .Please can u suggest me how i can increase the covering area.I will be thankful if u please give me the suggestion.

Aneesh

Hi,
Iam a student doing Btech project. Please give me a valid mobile detection circuit to detect the mobiles in the standby mode.

Hari

hello,

Can you please suggest me a mobile sniffer circuit when the mobiles are in standby mode. Its very urgent

tiray

where can we buy the circuit board?

SAm ?????????????

Plz give information about detaches Mobile No. and caller no. and reciver no.

muthuraman

Is there a possibility to get a more detailed discription on the circuitry operation to my email? please i am doing this as my college project so kindly send more detail on this circuit thank you

HSHJS

how can i detect a cell phone in standby mode .can you email me if you know

shaunak

could u plz give me the values of inductor...

Rishi

if we use schottky diodes then what is the range of operation?

Andrew

Thank you
I was about half way through designing something very similar using almost the same components.
once again
Thanks

Ghulam Abbas & Osama Ahmed

Hi! We are students of Electrical Engineering and we made ur cell phone detector as our project I m happy that its working actually we couldnt find diodes u mension se its range is very small could u please tell us any other diodes which can enhance its range Thank U

muthuraman

Hi,
Iam a student doing project. Please give me a valid mobile detection circuit to detect the mobiles in the standby mode.
Is there a possibility to get a more detailed discription on the circuitry operation to my email? please i am doing this as my college project so kindly send more detail on this circuit thank you

Abdul Khaliq

hi
i want to ask,what modification will b needed if i want to make this circuit change into a radar,and i can see the exact location of cell fone on the radar screen????

SRJ

Well, i also want to ask,what modification will b needed if i need to detect the postion of the cell phone. Glad if you could reply!

sara

hello,
i'm in a need of mobile circuit diagram for my project . please send some sites to find those circuits...

sharad

sir. i'm finding it difficult to get the output from this circuit.. please suggest me operating details..

chitra

i need to know the exact operation of this circuit ..kindly mail it to me ..

raghu

Sir, I had tried your mobile detector project , but it detect only when the call was comming. I want project to detect the mobile even call not comming. please send the circuit diagram

circuit_hacker

This is a diode-based version of a 1920s crystal radio circuit and the same warnings apply: It can pick up ANY strong RF signal nearby. I wouldn't place my hopes in this circuit's working as advertised except when it is held *next* to a GSM phone -- it needs a strong signal to work. If you're standing in the near field of an AM station it will probably pick that up, too.

maulik

give me circuit diagram

archana

garylui

may i know the circuit the out put is the LED ligth up???
if u detected signal then the out is what???

Ramesh

Sir,
I tried my best but not succedded yet in getting the output. can u plz tell me fm vr i cd get hw model of the cct at what cost rply urgent

GOGILAVANAN

CAN YOU FET ME WITH THE FULL DETAILS OF THIS PROJECT?

freddie hubalde

What is the maximum distance that this circuit can detect cellphone signals? I experienced this in most ICU's of the hospitals to prevent the frequency of the signals to interfere with the frequencies of the medical machines.

TASOS

WHAT ABOUTH IN PHONE STANDBY MODE?

ranjith

sir,
i am a student of electonics and communication engineering 3 year.i took cellphone detector as my mini project.will this circuit work???
what is the value of the inductance we should use,would u suggest anyother circuit instead?pls send details to This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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