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Brief features:

  • Operating frequency .......................................20-1300 MHz
  • Sensitivity....................................1 mV
  • The limits of localization.............................0,05-7 m
  • The voltage..............................4,5-9 In
  • Current consumption.....................................8 mA

Antenna type - telescopic

In the simple scheme indicator field(1) inherent in the very a big drawback, namely, low filtering at the input, due to which the device responds to electrical wiring in the room besides, he has a very low sensitivity 50 mV, therefore, low-power transmitters find difficult.

A little harder designs, but much easier to work searching device, shown in this figure, widely distributed organizations and private individuals.

The device is easy use to monitor work and low-power settings transmitting devices operating in a wide range of frequencies.

This device intended for local search for eavesdropping devices. It distinctive features are easy to repeat, reliability, small size. The drawback is a little reacts to extraneous radiation of radio from teleradiomerezha stations of cordless telephones. But this shortcoming is compensated by simplicity and cheapness of the indicator.

Input, induced telescopic antenna, enter the input RF amplifier, built on the VT1 transistor, and further, through the filter C1, L1, C3 to the detector-comparator DA1. The threshold the inclusion of the comparator set resistor R5. The signal comparator output 6 via inverter DD1.3 and the key VT2 controls square-wave generator pulses on the elements DD1.4, DD1.5 at 1 Hz, which, in its turn, includes generator sound frequencies on DD1.1, DD1.2.

Led VD1-two-tone. VD1.1 indicates power on green, VD2.2-about the discovery source of radio emission in red.

Instrument setup is to select the OS with DA1 probably a big factor gain. The distance at which the indicator light steadily to respond with the antenna length of 30 cm, the transmitter power of 1 mW must be at least 50 cm

The transistor can CT replace CT, with KT368 gain at least 150. Operational amplifier - COD. COD. Led ALS can be replaced conventional, type AL307, including them instead VD1.1 and VD1.2. Coil inductance has 19 turns reeled in a row on any resistor MLT 0,125, wire PEL is 0.1.

Author: tolik777 (aka Viper); Publication: www.cxem.net