Loudspeaking radio receiver with a bridge amplifier powered by free energy

While experimenting with different receivers and amplifiers powered by `free energy`, it was found that it is more convenient to connect the audio amplifier to the receiver by using only two wires for audio signals and supply voltage. This would allow to use the radio receiver with no switches, just connecting headphones to the output of the recei

ver. The schematic diagram of the receiver is shown in Figure 1. From the detector bridge the circuit is completely symmetric, the detector is connected to the amplifier by two wires (the terminals A and B) and the output of the amplifier is connected to the loudspeaker (the terminals C and D) by two wires. The resonant circuit of the receiver comprised the antenna capacitance and inductance of the coil L1. This solution provides a maximum power of the signal in the resonant tank circuit. The switch SA1 and the neon lamp HL1 are used to protect the receiver during thunderstorms. The static charge doesn`t build up in the antenna because the antenna connected to the ground through the coil L1. A bridge detector circuit (VD1 - VD4) is used in this receiver, it works very well for the inductive load. The detector connected to the antenna through the capacitor C1, this capacitor is matching impedances between them. Once adjusted for maximum voltage across the amplifier, the capacitor C1 may be replaced with a constant capacitor with proper value. The optimal capacitance of the capacitor C1 is about 47 pF for LW band. The output voltage of the detector is symmetric with respect to ground. Through the wires A and B the voltage passes from the detector to the input of the audio amplifier. At the input of the amplifier the voltage decomposes into AC and DC parts. The AC part feeds through the coupling capacitors C3 and C4 to the...

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