A lots of radio amateurs have an interest to power a simplest radio receivers with the `free energy`, i. e. the energy, taken by the receiver antenna directly from the air. The circuits described here can provide a radio reception using a loudspeaker. The question of how much power can get out of a signal from an antenna, and how to build a loudspe
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aking crystal set, was already discussed in the author`s articles [1, 2]. However the questions "how much power we need for loudspeaking reception " and "how to better use the power from the antenna ", still remain. According to the old reference books, to listening a voice of a broadcaster from the distance of 1 meter it takes the sound level of the loudspeaker about 60 dB. In this case, the radiated acoustic power is 12. 6 W. The necessary electrical power can be calculated by dividing the radiated acoustic power by the energy conversion efficiency of the loudspeaker. For the common loudspeakers the energy conversion efficiency is about 1%. Thus we get the electrical power about 1mW. It is interesting to calculate the required power for loudspeakers to get the sound level of 60 dB. The calculation results for the different loudspeakers are presented in table 1. From the table 1 we see that we need to use the high-efficiency loudspeakers. The acoustic design of the loudspeaker systems is very important, the bigger speaker cabinets is better. In the experiments the author used two loudspeakers type 4GT-2 in wooden cabinets with the enclosure volume of 50 liters. Horn loudspeakers has three times better efficiency because of the improved coupling efficiency between the speaker driver and the air and because of the directional characteristics of the produced sound waves. The simple and effective loudspeakers was built by...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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