The simplest radio receivers are not suitable for catching the FM band, frequency modulation. The townsfolk claim: hence the name. From the English letter FM we interpret: frequency modulation. A clear meaning, it is important for readers to understand: FM will not accept the simplest radio receiver assembled from rubbish. There is a question of necessity: the cell phone catches the broadcast. A similar feature is built into the electronic equipment. Far from civilization, people still want to catch the broadcast in the old-fashioned way - they almost said with dental crowns - to design efficient listening devices for their favorite programs. For free. ..
A simple radio detector: the basics of
The story touched on dental fillings for a reason. Steel( metal) is capable of converting ether waves into current by copying the simplest radio receiver, the jaw begins to vibrate, the bones of the ear detect a signal encrypted on the carrier. With amplitude modulation, the high frequency replicates the voice of the speaker, music, sound. The useful signal contains a certain spectrum, it is difficult for the non-professional to understand. It is important that when adding together the components we get a certain law of time, following which, the speaker of the simplest radio receiver reproduces the broadcast. On the failures, the jaw bone freezes, silence reigns, ear hears peaks. The simplest radio, God forbid, of course, get hold of.
The inverse piezoelectric effect changes the geometric dimensions of the bones according to the law of electromagnetic waves. Perspective direction: a man-radio.
The Soviet Union was famous for launching a space rocket, ahead of the rest of the world, with scientific research. Union times encouraged degrees. The luminaries have brought a lot of benefit here, - the design of radio receivers, - earn decent money over the hill. Films promoted intelligent, not well-off, it is not surprising that the magazines are full of various practices. A series of modern lessons on the creation of the simplest radios, available on YouTube, is based on magazines produced in 1970.We will be careful to move away from the traditions, we will describe our own vision of the situation in the sphere of amateur radio.
The concept of a personal computer was developed by Soviet engineers. Party leadership idea recognized as unpromising. Forces are given to the construction of giant computing centers. Overworked to master a personal computer at home. FunnyToday, the situation will meet more fun. Then they complain - America is shrouded in glory, prints dollars. AMD, Intel - have you heard? Made in USA.
The simplest radio do it yourself. The antenna is not needed, there is a good steady signal broadcast. The diode is soldered to the terminals of high-impedance headphones( computer discard), it remains to ground one end. In fairness, let's say, the focus will be with the good old D2 of the Soviet issue, the diversions are so massive that they will serve as an antenna. We will receive the earth in the simplest radio receiver by leaning one leg of the radio element on the radiator, which has been stripped of paint. Otherwise, the decorative layer, being the dielectric of the capacitor formed by the leg and the metal of the battery, will change the nature of the work. Try it.
The authors of the video noticed: there is a signal like that, represented by an unimaginable mix of rustling, meaningful sounds. The simplest radio receiver is devoid of selectivity. Anyone can understand, understand the term. When we set up the receiver, we catch the desired wave. Remember, discussed the spectrum. The ether contains a crowd of waves at the same time, catch the desired one, narrowing the search range. There is selectivity in the simplest radio receiver. In practice, it is implemented by an oscillatory circuit. Known from the lessons of physics, formed by two elements:
- Capacitor( capacity).
Let's take a while to study the details, the elements are supplied with a reactance. Due to this, waves of different frequencies have unequal attenuation, passing by. However, there is some resonance. The capacitor reactance on the diagram is directed in one direction, the inductance - in the other, and the frequency dependence is derived. Both impedances are subtracted. At some frequency, the components are equalized, the reactance of the chain drops to zero. There comes a resonance. Pass the selected frequency, adjacent harmonics.
Physics course shows the process of selecting the bandwidth of a resonant circuit. Determined by attenuation level( 3 dB below maximum).We present the calculations of the theory, guided by which a person can assemble a simple radio with his own hands. In parallel, the second diode is added to the second, included in the opposite direction. Soldered in series with headphones. The antenna is separated from the structure by a capacitor with a capacity of 100 pF.Here we note: the diodes are endowed with the capacity of the pn-junction, minds, apparently, have calculated the reception conditions, which capacitor is included in the simplest radio receiver, endowed with selectivity.
We believe that we will slightly deviate from the truth, saying: the range will affect the HF or HB region. Multiple channels will be received. The simplest radio receiver is a purely passive design, devoid of a source of energy, no great accomplishments should be expected.
A couple of words, why they discussed the remote corners, where radio amateurs crave experiments. In nature, physicists have observed phenomena of refraction, diffraction, both of which allow radio waves to deviate from the direct course. The first one is called the rounding of obstacles, the horizon moves away, giving way to broadcasting, the second - by the refraction of the atmosphere.
LW, SW and HF are caught at a considerable distance, the signal will be weak. Consequently, the simplest radio receiver discussed above is a touchstone.
The Simplest Radio Receiver with
Amplification In the simplest radio receiver design considered, you cannot use low-impedance headphones, the load resistance directly determines the level of transmitted power. Let's first improve the performance using the resonant circuit, then add the simplest radio receiver with a battery to create a low-frequency amplifier:
- The selective loop consists of a capacitor, an inductance. The magazine recommends that a variable capacitor with a tuning range of 25–150 pF be included in the simplest radio receiver; the inductance must be prepared in accordance with the instructions. A ferromagnetic core with a diameter of 8 mm is wound evenly with 120 turns, exciting 5 cm of the core. Copper wire coated with lacquer insulation with a diameter of 0.25 - 0.3 mm will be suitable. They gave readers the address of the resource where they calculate the inductance by entering numbers. Audience is available to independently find, using Yandex, to calculate the number of mH inductance. The formulas for calculating the resonant frequency are also well known; therefore, it is possible, remaining at the screen, to imagine the channel for tuning the simplest radio receiver. The training video suggests making a variable coil. It is necessary to extend inside the frame with the wound turns of wire, push in the core. The position of the ferrite determines the inductance. Calculate the range, using the help of the program, the craftsmen of Youtube suggest, winding the coil, to draw conclusions every 50 turns. Since there are about 8 taps, we conclude: the total number of revolutions exceeds 400. You change the inductance in steps, the exact tuning is carried out by the core. Add to this: the antenna for the radio is decoupled from the rest of the circuit by a capacitor of 51 pF.
- The second thing you need to know is that the bipolar transistor also has pn-junctions, and even two. Here is the collector is just appropriate to use instead of the diode. As for the emitter junction, it is grounded. Then to the collector directly through the headphones powered by direct current. The working point is not chosen, so the result is somewhat unexpected; patience will be needed until the device of the radio receiver is brought to perfection. The battery also greatly influences the choice. Headphone resistance is considered to be collector, which sets the slope of the output characteristic of the transistor. But these are subtleties, for example, the resonant circuit will also have to be rebuilt. Even with a simple replacement of the diode, not like the introduction of the transistor. That is why it is recommended to conduct experiments gradually. A simple radio without amplification will not work for many at all.
And how to make a radio that would allow the use of simple headphones. Connect via a transformer, similar to what is in the subscriber point. A tube radio is different from a semiconductor in that in any case it requires power to operate( heat filaments).
Vacuum devices for a long time come to the mode. Semiconductors are ready to take immediately. Do not forget: germanium does not tolerate temperatures above 80 degrees Celsius. If necessary, consider cooling the structure. At first, this is necessary until you find the size of the radiators. Use fans from a personal computer, processor coolers.