Portable, with AM radio station. Scheme, description

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Portable, with AM radio station. 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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Technical data:

Supply voltage - 9 V ("Krona" or 7D - 0,15)
Communication range between the same type of pair of radio stations 1,5 km
Current consumption in receive mode 10 mA in transmit mode 35 mA.
Telescopic antenna 700 - 800 mm
Housing dimensions 145 x 65 x 37 mm

(click to enlarge)

The radio station is designed for two-way radio communication in the range of 26 - 967 MHz with amplitude modulation. The radio station is built according to a transceiver circuit. The signal from the antenna is fed to the ULF input on transistors VT27,281, VT1, then to the super-regenerative detector on VT2 and further, through the contacts of the switch TX, RX - to the ULF input on transistors VT3 - VT4 and after amplification - to the DEMSh7 A capsule, which is used in the mode reception as a loudspeaker. In the transmitter master oscillator (VT1 transistor), a quartz resonator at a frequency of 9 MHz is excited at the third mechanical harmonic, i.e. 9 MHz is the tuning frequency of the L27C5C24 circuit. Through the coupling coil, the signal is fed to the input of a power amplifier based on a VT25 transistor operating in class "C" mode, and through the p-loop and extension coil LI - to the antenna.

The modulating signal from the transformer Tr1 is fed to the collector VT8. The same DEMSh1 A is used as a microphone after switching.

The elements of the radio station are placed on a printed circuit board made of one-sided foil fiberglass with a size of 63 x 113 mm. The power wiring to the circuit elements from the TX, RX switch is made with insulated conductors. The wires going to DEMSh1A and from the Tr1 output are shielded.

Tuning a radio station has no special features, the establishment of a super-regenerative detector has been repeatedly described in the Radio magazines in the radio control sections of models.

The DEMSh1A should be attached to the case through a foam rubber gasket, having previously removed the plastic case from the capsule. These measures make it possible to avoid acoustic feedback with transformer Tr1.

Inductors LI, L6, L7 used type DO.1 - 50 μH. Coils LI, L3, L5, L8 are wound on frames with a diameter of 8 mm. L3 has 7 turns of PEV-0,5, LI-14 turns of PEV-0,35. L5 - 10 turns of PEV-0,5, L4 is wound over L5 and has 3 turns of PEV-0,35, L8 - 8 turns of PEV-0,5. Switch RX-TX - P2K type. Transformer - from receivers "Neiva", "Jupiter", etc. It has 650 turns of PEV-0,09 in the primary winding and 900 turns of PEV-0,09 in the secondary.

Author: V. Ruslyakov (UA4ABD); Publication: N. Bolshakov, rf.atnn.ru

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