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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Perpetual radio. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / radio reception In an article published in Radio No. 1 for 1997 About feeding radio receivers with free energy a theoretical justification was given for obtaining the maximum power of the detected signal from the antenna. Guided by the considerations given in this article, its author conducted a series of experiments confirming the possibility of building a detector receiver that provides loud-speaking reception of sufficiently powerful broadcasting stations. We decided to acquaint our readers with their results. The schematic diagram of the loud-speaking detector receiver used in the experiments is shown in fig. 1. Its input oscillatory circuit is formed by the capacitance of the antenna WA1 and the inductance of the coils L1, L2. The detector is made on a germanium point diode VD1 and, through a trick, the transformer T1 is loaded onto the dynamic head BA1. In series with the primary winding of the transformer, an avometer P1 is connected, shunted by a blocking capacitor C1.
At first, the experiments were carried out in a city apartment located on the top floor of a nine-story large-panel building on the eastern outskirts of Moscow. The functions of the antenna were performed by a roof-mounted antenna for an amateur band of 10 m, which is a 2,5 m long rod with three counterweights of the same length. The pin is fixed on a wooden mast and isolated from the roof. The center wire and the shielding braid of the drop cable were connected together and connected to the antenna jack of the receiver. The result is a kind of vertical antenna with a length (together with a decrease) of about 12 m with a capacitive "umbrella" at the top. The central heating pipes served as grounding. As L1, L2, long-wave coils of magnetic antennas were used, placed on separate magnetic circuits from portable receivers (their brand does not matter, since these coils of almost all receivers have the same windings). The circuit was tuned to the frequency of the radio station by moving the magnetic circuit inside the coils, and in this case a very wide tuning range was provided. Two series-connected coils are needed only to increase the total inductance of the circuit, which would make it possible to tune in to the longest-wave radio station operating in the Moscow region at a frequency of 153 kHz. The T-III-3M output transformer was used from a subscriber broadcast loudspeaker, a 3GD-1 dynamic head with a voice coil resistance of 8 ohms. Avometer R1-Ts4317. In the DC voltmeter mode, this device measures the detected voltage at "idle" (the circuit of the primary winding of the output transformer is actually open), and in the milliammeter mode - the detected current. At the end of the measurements, the avometer should be turned off, and the capacitor should be closed. The loudest radio stations were heard at frequencies 171 (the former name of the Comintern) and 918 kHz ("Open Radio"). The latter transmits from the Balashikha radio center and is better heard due to its proximity to the reception point. The detected voltage, measured at idle, was in both cases about 7 V, and the detected current was 45 and 160 µA, respectively. The greater current provided by the radio station "Open Radio" is explained by the lower resistance of the input circuit at a higher frequency and, as a result, greater efficiency. However, the volume of the signals of both received radio stations was sufficient to sound a nine-meter room. The next series of experiments was carried out on a garden plot located in the northwest of the Moscow region near Solnechnogorsk (65 km). Reception was carried out on an L-shaped antenna with a horizontal part length of 20 and a suspension height of 8 m. A free-standing birch and a wooden pole served as antenna supports (Fig. 2), and necks from polyethylene bottles served as insulators. For grounding, pipes of a water well for a hand column were used, deepened by about 5 m. The antenna itself was made of a rather thin wire (PEL 0,5) wound from an old transformer, and an uninsulated wire with a diameter of 3 mm was used for grounding. From the garden house to the well (-12 m) it was laid directly on the ground (Fig. 2).
Such an antenna received well the signals of radio stations at frequencies 153 ("Youth Channel"), 171 ("New Wave") and 261 kHz ("Radio of Russia"). Moreover, the last radio station was received with the highest volume. For it, the detected voltage, measured at idle, was 2,7 V, and the detected current was 0,3 mA. It is known that the power given by the signal source to the matched load is Рsgl=Uхх*Iкз/4 (where Uхх is the open-circuit voltage and Iкз is the short-circuit current). This means that when receiving this station, the receiver is able to develop a DC power of about 0,25 mW, which corresponds, for example, to a supply voltage of 1,5 V at a current consumption of 0,17 mA. And this is quite enough to power a small ultra-economical transistor receiver. Author: V.Polyakov, Moscow
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