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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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GIR for CB band. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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A simple device - a heterodyne resonance indicator (GIR) - will greatly simplify the adjustment of equipment and tuning of the antenna-feeder path. By replacing the frequency-setting elements, this GIR can be "overtaken" to any amateur band.

The GIR is a soft-excited LC oscillator that is very sensitive to external influences. If you bring, for example, a loop coil to the GIR coil, then the generator mode will change. In particular, the RF voltage on the generator circuit will decrease. The maximum "suction" of energy will occur when its frequency coincides with the resonant frequency of the studied oscillatory circuit. By registering in one way or another a change in the GIR generator mode, the resonant frequency of the circuit, antenna, feeder line, etc. is determined.

The scheme of the device is shown in fig. 1. It consists of an LC oscillator (VT1, L1, C1-C3, R1), a detector (VD1, C4, R2), a DC amplifier (VT2, R4) and a dial indicator PA1.

GIR for CB band

The printed circuit board is shown in fig. 2. It is made of double-sided foil fiberglass with a thickness of 1,5 mm. The foil on the side of the parts is used only as a common wire: in the places where the conductors pass, circles with a diameter of 2 ...

GIR for CB band

Coil L1 is a four-turn flat frame laid on the board from the side of the parts. It can be glued, sewn, etc. The wire is practically any, it is only important that its outer diameter (in terms of insulation) is within 0,6 ... 0,75 mm. Withdrawal - from the first turn.

Resistors R1, R3, R4 can be MLT-0,125, R2 - SP3-38a. Capacitor C1 - KPK-MN, C2 - KD or KT, C3-C5 - KM-6. As PA1, you can use any pointer microammeter for 100 ... 500 μA.

Setting up the generator comes down to setting the operating frequency range within 25 ... 30 MHz by selecting capacitor C2. You can control the frequency of the generated signal with a frequency meter (the connection point is the outlet of the L1 coil) or on the scoreboard of a multi-grid CB radio station, the antenna of which must be placed next to the generator.

In the absence of any external influences, the resistor R2 sets the arrow PA1 to almost the entire scale. The measurement is carried out as follows: the GIR coil is brought closer to the desired element of the antenna system - a vibrator, a counterweight, a director - and the position of the rotor of the capacitor C1 is found, at which the readings of PA1 are minimal. Now it remains to find out what frequency this minimum corresponds to. The easiest way to do this is with a multi-grid portable radio. Put into scan mode, it will simply "stop" at his frequency.

Author: Yuri Vinogradov, Moscow

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