The simplest device for finding radio bugs. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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The simplest device for finding radio bugs. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling

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The simplest device for finding "bugs" Even if you have nothing to fear, but you would like to find out if someone is spying on you with the help of eavesdropping radio equipment, assemble the circuit shown in Fig.1.

(click to enlarge)

The device is a simple radio wave detector with sound indication. With it, you can find a working microtransmitter in the room. The radio wave detector is sensitive to frequencies up to 500 MHz. You can adjust the detector when searching for working transmitters by changing the length of the telescopic receiving antenna.

The telescopic receiving antenna perceives high-frequency electromagnetic oscillations in the range up to 500 MHz, which are then detected by a VD1 diode of the D9B type. The high-frequency component of the signal is filtered out by the inductor L1 and capacitor C1. The low-frequency signal enters through the resistor R1 to the base of the transistor VT1 type KT315, which leads to the opening of the latter and, as a result, to the opening of the transistor VT2 type KT361. At the same time, a positive voltage appears on the resistor R4, close to the supply voltage, which is perceived by the logic element DD1.1 of the DD1 microcircuit of the K561LA7 type as the level of a logical unit. This turns on the pulse generator on the elements DD1.1,DD1.2, R5 and C3. From its output, pulses with a frequency of 2 kHz are fed to the input of the buffer stage on the elements DD1.3, DD1.4. The load of this cascade is a sound piezoceramic transducer ZQ1 type ZP-1, which converts electrical vibrations with a frequency of 2 kHz into acoustic ones. In order to increase the sound volume, the ZQ1 converter is connected between the input and output of the DD1.4 element of the DD1 chip. The detector is powered by a 9 V current source through a parametric stabilizer on the elements VD2, R6.

The detector uses MLT-0,125 type resistors. Diode VD1 can be replaced with GD507 or any high-frequency germanium. Transistors VT1 and VT2 can be replaced by KT3102 and KT3107, respectively. The VD2 zener diode can be any with a stabilization voltage of 4,7-7,0 V. The ZQ1 piezoceramic converter can be replaced with ZP-22. Inductance L1 - 1 miHenry.

It is best to tune the detector using a high-frequency generator. Connect an insulated wire - antenna to the output of the generator, and place the detector antenna parallel to it. This way you loosely couple the detector to the generator. Explore the entire radio band from 500 kHz up to the point where the detector stops receiving radio waves. Notice how the sensitivity of the detector changes with frequency.

Publication: cxem.net

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