Electronic Eavesdropping Devices Detector

[eplanet]

hi audioguru
do u know any circuit for detecting secret  digital camera?

 

[audioguru2]

A digital camera has a very low level digital signal inside. It would be difficult to detect it.

 

[eplanet]

hi audioguru
i am changing this circuit that u said me but not have result always have  continously sound  i have to build a new circuit of this circuit do u have any idea about this circuit or any changing on it???
thanks

 

[audioguru2]

The opamp with a DC gain of 4,545 is rediculous. The voltage-controlled-oscillator is the same as the one in the datasheet for the old LM324 quad opamp.

Replace the MC3403 quad opamp and the problem will be better, it will be worse or it might not have a problem anymore.

 

[eplanet]

hello audioguru
please tell me that when i build a Eavesdropping device(this circuit) for start after build what hapen after press the on swich (for start).

 

[audioguru2]

hello audioguru
please tell me that when i build a Eavesdropping device(this circuit) for start after build what hapen after press the on swich (for start).

I don't think the project works:
1) The value of R18 is too low.
2) C2 should be a 1k resistor.
3) The AM detector circuit and DC amplifier's input look weird.
4) The DC amplifier amplifies its own DC input offset voltage which messes-up the voltage-controlled audio oscillator.

If it works correctly then it will pickup all FM and TV stations and taxi cab radios in town.
If there is no RF then the VCO should be quiet. With a low amount of RF then it should make a low frequency growling sound. Its pitch should get higher with stronger RF.

 

[eplanet]

hello
V (input): 7.25v
pin1 : 3.54v
pin7: 1.97v
pin8 : 3.73v
pin14: 3.25v
TR1: collector: 4.55v
this project all of times have alarm even when i adjusting PT to right and left.
what can i do ?

 

[audioguru2]

The project doesn't work. The first opamp amplifies its own input offset voltage.

 

[eplanet]

what can i do?

 

[audioguru2]

what can i do?

You can cry.
You picked a circuit that doesn't work.

 

[eplanet]

what is the mining of offset exactly ?

 

[audioguru2]

what is the meaning of offset exactly?

Input offset voltage of an opamp is an error in the balance of its inputs which is amplified by the opamp and causes a DC output voltage when the inputs have the same voltage. Most opamps have a max input offset voltage of 8mV. Single opamps have terminals where a trimpot can be connected to cancel input offset voltage.
Modern expensive opamps are trimmed with a laser when they are made for extremely low input offset voltage. They usually need a dual polarity supply. 

 

[eplanet]

hello
i have a question
i am using BFR91  replace for BFR90 and for NTE112 replace similar to BA481.
do u think these  components good work with together ? because my project alarming sequence. 

 

[audioguru2]

With no radio signal picked up by the circuit, the output pin 1 of opamp A1 is supposed to be 0V so the voltage-controlled-oscillator that is made with the other opamps has no sound output.

Your A1 opamp amplifies its own input offset voltage and makes its output voltage high enough for the voltage-controlled oscillator to make sound.

The RF transistor and detector diode don't affect the offset voltage. They don't operate at high enough frequencies to pickup modern cell phones.

 

[eplanet]

hello
i am making a eavesdropping devise and it is work but this project sensitive to anything very high. specially to any metal and sensitive to computer
and for this project 9v battery don't good working.
please tell me what can i do ?
i wont sensitive to any metal i want sensitive to mobile and eavesdropping devices.

 

[audioguru2]

Yes, the Eavesdropping Devices Detector project has an untuned input so it picks up all high frequency signals. A computer makes high freqiency signals so it will detect them.
A piece of metal doesn't make high frequency signals so the circuit should not detect anything from it.

The supply current is very low so a 9V alkaline battery should last for a long time.

 

[AN920]

i want sensitive to mobile and eavesdropping devices.

Many cheap bugging devices work in the commercial FM band so that may cause problems detecting them out of all the other stations.

 

[audioguru2]

Many cheap bugging devices work in the commercial FM band so that may cause problems detecting them out of all the other stations.

The other stations are all the FM stations, all the VHF and UHF TV stations and all the taxi cab radios.
The Eavesdropping Devices Detector picks up a computer's interference so it might even pick up radiation from a radio and a TV.

 

[eplanet]

hello
this is eavesdropping device detector that i was build it. these green LED's that u can see is VU meters with LM3915.
tell me your idea.

View attachment 40462

 

[audioguru2]

Hi Eplanet,
Your project looks very nice.
Why are all the LEDs on? Is it picking up a very strong signal?