Wireless transmitter circuit diagram

The radio remote control circuit uses radio signals as remote control instructions to complete various specified actions according to regulations. Amateur frequency bands include 28.0~29.7MHz, 50~54MHz, 144~148MHz and 420~448MHz. The higher the frequency, the higher the requirements for devices. This article first introduces the radio remote control composed of discrete components in the 28.0~29.7MHz range. unit circuit.

The radio remote control circuit consists of two parts: a radio transmitter and a receiver. The transmitter can be divided into non-modulation type, amplitude modulation type, frequency modulation type and phase modulation type according to the modulation method. The receiver can be divided into three types according to the receiving method. Direct amplification type, super regenerative type and super heterodyne type, etc. This article introduces modulation-free and amplitude-modulated radio remote control transmitters, and then introduces the unit circuit of a radio remote control receiver.

radio remote control transmitter

Figure 1 is the simplest inductive three-point radio remote control transmitter. The oscillation frequency is determined by L2 and C2. L1 and L2 are wound on the same Φ8 coil tube with a magnetic core. L2 is wound around 10 turns. The triode is connected to the tap of the second turn. VT collector, L1 has 5 turns. This circuit is non-modulated. Press the button SB, the circuit will start to vibrate, and the antenna will radiate high-frequency carrier waves into the air. The transmitting power of this circuit is only tens of milliwatts, and the remote control range can reach tens of meters. VT is an ultra-high frequency tube with a cut-off frequency above 200MHz. Such as 9018, 3DG12 type, etc.

Figure 1 The simplest inductive three-point radio remote control transmitter

Figure 2 is a capacitive three-point oscillator with a grounded base. Use it as a radio remote control transmitter. The circuit works stably and the oscillation frequency can be higher, but the output power of the circuit is slightly smaller. L2 and L3 are high-frequency choke coils, which can be used Wrap Φ0.1 enameled wire around the resistor with a resistance of 1MΩ or above for 50 turns, and then solder the two wire ends to the two pins of the resistor. The purpose of setting up a high-frequency choke coil can effectively reduce the damage caused by manually pressing the switch SB. Human body induction phenomenon, this circuit is also non-modulated.

Figure 2 Capacitive three-point oscillator with base grounded

Figure 3 is a push-pull radio remote control transmitter with a large output power. The output power can reach tens to hundreds of milliwatts, and the remote control distance can reach hundreds to thousands of meters. It is also unmodulated and directly uses high-frequency carriers. As a remote control command, in order for the circuit to work well, the characteristics of the two tubes VT1 and VT2 are required to be as consistent as possible. L2 can be wound with 6 turns of Φ1 enameled wire. The coil diameter is 12~15mm. It is wound without a skeleton. The center tap is connected to the power supply. Both ends of the coil are directly welded to the two welding tabs of the ceramic trimming capacitor C2. L1 is wound with 2 turns of the same number of wires. , wound between L2.

Figure 3 Push-pull radio remote control transmitter with larger output power

Figure 4 is a non-modulated radio remote control transmitter using quartz crystal frequency stabilization. The circuit features are easy starting, high frequency stability, simple structure, etc. B uses a 28.750MHz quartz crystal packaged in an aluminum shell. The emission of each of the above circuits The antenna can be a rod antenna used for transistor radios, and the length can be between 0.6 and 1.5m. Antennas with different lengths have a slight impact on the transmission distance. The optimal length is 1/4 of the wavelength of the high-frequency carrier.

Figure 4 Unmodulated radio remote control transmitter using quartz crystal frequency stabilization