ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Receiver without power. Encyclopedia of radio electronics and electrical engineering Encyclopedia of radio electronics and electrical engineering / radio reception In some places (duty room, workshop) it is desirable for the radio to work quietly (as a background), but around the clock. The battery in this mode will have to be changed often, and leaving the AC adapter on all the time is risky. I propose a radio receiver (Fig. 1), which does not require a power source. In fact, this is a detector receiver with a full-wave detector, only the detector itself is not diode, but transistor. The fact is that the resistance of the open collector junction of the transistor is less than the direct resistance of the diode. The result is a more efficient detector and the receiver sounds louder.
In order to have a radio signal at the input with an amplitude sufficient for the operation of the detector receiver, it is necessary to use a good external antenna, for example, from a copper winding wire. Its diameter is not critical and is selected for reasons of mechanical strength (0,5 ... 2 mm). The antenna can be made in the form of an inclined beam. With its length of 52 m and height at the top of 16 m above the ground, the receiver receives stations of medium and long waves at a distance of 40 ... 50 km quite loudly even on low-impedance phones. And on high-resistance capsules ("Ton-1") you can hear more distant radio stations. An even louder sound is obtained if a dynamic head with a power of 2 ... 4 W (4GD-8E) is connected to the output through a step-down transformer with a transformation ratio of 10 ... 12. Transformer core - Sh8x10, made of permalloy. The primary winding contains 1800 turns of PEV wire 0,1 mm, the secondary - 160 ... 180 turns of PEV 0,59 mm. In this case, the sound is heard at a distance of several meters from the receiver (of course, everything depends on the power of the received radio station and the distance to it). This receiver requires good grounding. From the first floor, it is better to stretch the wire to a metal object buried in the ground to a depth of 1,5 ... 2 m (an old bucket). In another case (on the upper floors), you can connect to the heating pipes or the grounded circuit of the house itself. The receiver circuit uses transistors (it is desirable to choose a pair) with a gain of 100 ... 150 such as GT108G, GT109G or GT309B. As a receiver housing, a broadcast loudspeaker is convenient, along with its speaker and output transformer. The input transformer T1 is wound on a round ferrite rod with a diameter of 8 ... 10 mm. Suitable parts from an old transistor receiver ("Alpinist", "Ocean", etc.): housing, speaker, output transformer (half of its primary winding is turned on if the output is push-pull), a variable capacitor and a magnetic antenna on a ferrite core (on coils of medium and long wave ranges are left on it). Their data: DV - wire PELSHO 0,16 mm - 120 turns; SV - PEV 0,31 mm - 36 turns. When self-manufactured, winding is carried out on a paper sleeve, dressed on a rod, so that the coils move along the core in search of the place of greatest volume.
Winding length for DV - 28 mm (limited by paper cheeks), for SV - 16 mm (ordinary). Particular attention should be paid to winding II. It is located in the center of the rod and has 30 turns with a tap from the middle (2 sections of 15 turns) of 0,31 mm PEV wire. Windings III and IV are wound on the respective sections over coil II. Each of them contains 10 turns of PEV wire 0,44 mm. The winding length of one section is 7 mm. The ends of the coils are "caught" with glue. The location of the coils on the rod is shown in Fig.2. If the receiver output is connected to an AF amplifier, a more sensitive receiver with increased volume will be obtained. True, in this case one cannot do without a power source, but the purity of the sound will pleasantly surprise you, since the noise and whistles characteristic of a superheterodyne receiver are not heard. Author: E.Ryabichko, st.Kelermesskaya, Adygea. See other articles Section radio reception. Read and write useful comments on this article. Latest news of science and technology, new electronics: Artificial leather for touch emulation
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