Radio Magazine, May, 1997
In the article "About powering radio receivers with Free Energy " published in the May 1997 issue of the Radio magazine was given a theoretical basis to obtain maximum power of rectified signal from antenna. Using some considerations from that article, the author performed a set of experiments that confirmed possibility to build a circuit of crystal radio that can provide loudspeaking reception of powerful radio broadcasting stations. The results are described below.
The circuit diagram of the crystal radio that was used for experiments is shown in Figure 1. Its input resonant tank is formed by the capacity of antenna AE1 and inductance of coils L1, L2. The germanium diode D1 is used as a detector, and with the transformer T1 it is loaded by the loudspeaker LS1. The multimeter A1 is connected in series with the primary winding of the transformer, and it is blocked by the capacitor C1.
Fig.1. The circuit diagram of the loudspeaking crystal radio receiver.
At the beginning, experiments were performed in the city apartment, located at the upper floor of the 9-floor panel building at the eastern outskirt of Moscow. An antenna for amateur 10 meter band was used in these experiments. It's made of 2.5 meter rod with three counterweighted rods of the same length. The antenna rod is attached to a wooden mast, and is insulated from the roof. An inner conductor of the coaxial cable is shorted to its conducting shield and connected to the antenna jack J1 of the radio receiver. As a result, the whole system worked as an umbrella antenna of 12 meter long with a capacitance at the top of the antenna. The water heating system was used as a ground (heating pipes were connected to the jack J2).
Long wave magnetic loop antenna coils were used as inductance coils L1, L2 - this is standard coils for portable radios. To tune to a radio station, just move ferrite rods inside coils, the tuning range is quite wide. Two coils are used here only to increase the whole inductance of the resonant tank, it will make possible to tune to the 153 kHz radio station, this is the lowest-frequency radio station in the long wave band working in the Moscow region.
The audio transformer T1 (model T-III-3M) turns ratio is about 35, the resistance of the loudspeaker LS1 is 8 Ω. When the multimeter is used as a voltmeter, it measures the idle voltage across the detector, and when it is used as an ammeter, it measures the detected current. After measurements are done, disconnect the multimeter from the circuit, and short the capacitor C1.
Two long wave radio stations that broadcasted on frequencies of 171 kHz and 918 kHz were the loudest. In both cases, the idle voltage was about 7 Volts, and the detected current - 45 μA and 160 μA correspondingly. The higher current in the second case is because the resonant tank has a lower impedance at the higher frequency, therefore it has a higher efficiency. Anyway, in both cases the audio volume was enough to be heard in 10 square meter room.
Fig.2. Inverted "L" - shaped antenna and the ground, connected to the water well.
The next set of experiments was performed at a garden plot, located in the north-west part of the Moscow region, 65 km from the city. An inverted "L" - shaped antenna was used for radio reception. It has a horizontal part of 20 meter, and a vertical part of 8 meter long. The antenna was installed on a pole and a tree (see the Figure 2.). Bottlenecks were used as insulators. A water well was used for grounding, its pipes are buried about 5 meters deep. The antenna is made of 0.5 mm (AWG #24) wire, the ground wire is 3 mm in diameter (AWG #9). The ground wire was lying on the ground along the way from the house to the well (12 meter).
This antenna provided a good reception of several local radio stations operating on frequencies 153 kHz, 171 kHz, and 261 kHz. The last radio station was the loudest one, the idle voltage was 2.7 Volts (without the load), the current was 0.3 mA.
It is known that the power at the matched load is
Pm = (Ui * Is) / 4,
where Ui - idle voltage;
Is - short circuit current.
It means that the receiver provides the power of 0.25 mW for that radio station, it corresponds to the power supply voltage of 1.5 Volts with the consumption current of 0.17 mA. That's quite enough to power up a small transistor radio receiver.
V. Polyakov, Moscow