Player - for two. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Player - for two. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Audio equipment

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Walking with a friend, you often want to listen to the player together. But connecting a second pair of headphones to it is inconvenient. So I decided to use the radio channel. To do this, I added a radio transmitter to the player, and gave a radio receiver with a VHF (FM) range to a friend. The power of the radio transmitter (see figure), of course, is small, but it is enough to receive the signal from the AF player at a distance of several meters.

Player - for two

The input of the radio transmitter is connected to the output of the player in parallel with the headphones. The variable resistor R1 regulates the level of modulation, and hence the volume of the sound and its quality. The RF generator, assembled on a transistor, generates oscillations with a frequency of about 100 MHz, which depends on the parameters of the L1C4 circuit.

Through the communication coil L2, the modulated (in frequency) oscillations enter the antenna WA1 - a piece of wire of short length (15 ... 20 cm), if the receiver is located close. In the case when a bicycle ride is supposed, it is best to use a bicycle frame as an antenna and connect the wire to it.

In addition to the transistor indicated on the diagram, you can use KT306G, KT306D or another low-power microwave structure npn or pnp (in this case, you need to change the polarity of the power source). Fixed resistors - MLT0,125, variable - any small-sized, capacitors KM6 (C2), K53-14 (C6), KLS, KT (others). Coils are wound with PEV or PEL wire on a frame with a diameter of 7 and a length of 10 ... 12 mm, glued from cardboard or thick paper. Coil L1 should contain 6 turns, L2 - 3 turns. The coils are placed side by side.

The details of the radio transmitter are mounted in a small case by surface mounting or on a printed circuit board. The case is fixed on the player's case. In the case of powering the radio transmitter from the source of the player, you should install an RC filter, shown in the diagram below on the right.

Author: E.Petrosyan

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