Transmitter course courseware

The principle of radio receiving and transmitting is that the transmitter sends out current of different frequency and wavelength according to the requirements of sending out information, so that the electrons on the transmitting antenna change the direction of rotation according to the frequency, the tail of its magnetic line breaks off and pops up, the two ends of its moving magnetic line constantly attract free space lead particles to grow and form different frequencies and waves in all directions of the space Long density plane "wave". When the "wave" touches the radio receiving antenna, it drives the free electrons on its surface to rotate around the antenna according to the frequency and wavelength of the "wave", and then forms an alternating current. After being amplified, this weak current becomes the receiving information of the transceiver.

This introduction of this kind of small transmitter is a very good small production of science and technology, the principle is very simple. Two dry batteries are connected in series with a key switch, a resistor and an LED lamp. Press the key, the circuit is connected, and there is current passing through the LED lamp, which will light up. At the same time, the sounder is powered on. Release the button, the current disappears and the sending byte is completed. We know that the telegram sends information by the length of sound (or signal). As for our small transmitter, the long tone or short tone can be distinguished by controlling the sound interval according to the length of switching time, so as to achieve the purpose of sending information.

Experimental cognition:

Battery box: as the name suggests, the box for installing fixed battery is the battery power output device

LED lamp: LED (light emitting diode), a kind of solid-state semiconductor device, can directly convert electricity into light. The heart of LED is a semiconductor chip. One end of the chip is attached to a bracket, the other end is negative, and the other end is connected to the positive of the power supply, so that the whole chip is encapsulated by epoxy resin. The semiconductor chip is composed of three parts, one is p-type semiconductor, in which the hole dominates, the other is n-type semiconductor, in which there are mainly electrons, and the middle is usually a quantum well with one to five cycles. When the current acts on the chip through the wire, the electrons and holes will be pushed into the quantum well. In the quantum well, the electrons and holes compound, and then the energy will be emitted in the form of photons, which is the principle of LED light-emitting. The wavelength of light, the color of light, is determined by the material that forms the p-n junction.

Switches: devices for switching on and off the power supply

Resistance: the obstruction of conductor to current is called resistance! Factors affecting the resistance, such as length, cross section, area, material, temperature, and so on. For general metal materials, the resistance increases with the increase of temperature.)

Sounder: a very simple principle is to use one port to output square wave, which will generate sound when input into the buzzer. By controlling the frequency and time of square wave, simple music can also be generated

Experimental steps:

1. Prepare and know the experimental equipment: screw hole plate, switch, resistance, wire, LED light, battery box, sounder, screwdriver, diagonal pliers.

Experiment report:

The principle of radio technology is that changes in the strength of the current in the conductor will produce radio waves. Using this phenomenon, information can be loaded on the radio wave by modulation. When the electric wave propagates through space to the receiving end, the electromagnetic field changes caused by the electric wave will generate current in the conductor. By demodulating the information from the current change, the purpose of information transmission is achieved.