Equivalence of electric and magnetic antennas. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Antennas. Theory
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Not much time has passed since the publication of [1], and now new results have appeared, this time experimental. Having climbed onto the roof of a country house, mentioned in [2], allegedly for the purpose of repairing it, and taking advantage of the fact that the neighbors (the owners of the lower floor) were absent, the author decided that science was more important, and extended a large loop antenna from PEL 0,7 wire.
From the entrance to the attic window, the antenna wire passed through the roof ridge to the bushes on the other side of the house, then straight along the ground (more precisely, along the grass at a height of 10 ... 20 cm above the ground) under the window and vertically up into the window, as shown in Fig. . 1. In the same figure, for comparison, a permanent electric antenna 10 ... 12 m long is also shown, stretched to a tree growing nearby.
The frame magnetic antenna had an area almost equal to the area of an imaginary vertical plane under the electric antenna - about 80 m2. Initially, both antennas were tuned in resonance to the frequency of the radio station "Radio Russia" with a frequency of 873 kHz, the electric one - with a high-quality coil, the magnetic one - with a double variable capacitor (KPI) 17 ... 510 pF, both sections of which were connected in parallel. When measuring the high-frequency voltage, values of 17 V were obtained on the coil of the electric antenna and only 1,6 V - on the KPI magnetic. But such a discouraging result should not confuse - it is necessary to compare the powers delivered to the receiver, which, in accordance with the conclusions of [1], should be the same.
The receiver installed in the attic was not the "latest model", even from among home-made ones - its diagram is shown in fig. 2 in [2]. All these years, the receiver has worked practically without turning off (why - it does not consume electricity!). The power supply voltage of the amplifier, measured on the storage capacitor when working with an electric antenna, was about 5 V.
The connection diagram of the receiver to the magnetic antenna is shown in fig. 2.
In this case, the supply voltage was about 3 V, and since the current consumed by the amplifier remained practically unchanged (about 0,3 mA), we can assume that the power given off by the magnetic antenna was about 70% of the power of the electric antenna. This loss is apparently explained by the lower height of the frame suspension, the large volume of wooden structures of the house inside it, as well as inconsistency with the amplifier: the frame should have been loaded more strongly by increasing the amplifier current. The sound volume with both antennas was almost the same - a little louder with the electric one.
Another interesting experiment. After connecting the electric antenna to the upper (according to the scheme) terminal of the magnetic antenna (without grounding), the voltage increased to 3,8 V. The idea of connecting the electric and magnetic loop antennas does not belong to the author - it was previously independently expressed by V. Besedin from Tyumen and N. Turkin from St. Petersburg. Apparently, it deserves attention and requires further study.
Thus, the suitability of large loop antennas for detector reception can be considered fully proven.
Literature
- Polyakov V. Equivalence of electric and magnetic antennas. - Radio, 2002, No. 11, p. 16, 17.
- Polyakov V. Loud-speaking "detector" receivers. - Radio, 2000, No. 7, p. 22, 23.
Author: V.Polyakov, Moscow
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