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RADIO ON THREE TRANSISTORS.

RADIO   ON   Three   TRANSISTORS.

N. Marushkevich , Minsk

The radio station is designed for two-way communication in the range of 27 MHz with amplitude modulation. It is assembled according to the transceiver scheme. The cascade on the transistor VT 1 serves as a receiver and transmitter. Amplifier transistors VT 1 and VT 2 in receive mode amplifies the signal allocated by the receiver, and in transmit mode modulates the carrier .

When installing special attention should be paid to the location of the capacitors C10 and C11. They are used to prevent self-excitation. If self-excitation still occurs, then you must connect an additional several capacitors of the same capacity.

About customization. She is very simple. First, with the help of a frequency meter , the transmitter frequency is set, and then the receiver of another radio station is tuned for maximum noise suppression and highest signal loudness. The coil L 1 adjusts the transmitter, and the coil L 2 tunes the receiver.

TECHNICAL DETAILS:

Supply voltage -   9-12 V.

The communication range in the open area is about 2 km .

The receiver current consumption is 15 mA,

transmitter - 30 mA.

Telescopic antenna -   0.7- 1m .

Case dimensions -   140x75x30 mm.

Tr 1 - any small output transformer.

Ba 1 - any suitable in size speaker with a winding resistance of 8-10 ohms.

DR 1 - DPM-0,6 or self-made: 75-80 turns of the sew 0.1 on the resistor MLT 0.5 W - 500 kOhm.

The remaining parts are of any type.

The coils are wound on frames with a diameter 8 mm and contain 10 turns of wire sew 0.5.

Printed and circuit boards -   in fig. 2     ð