Hand-held interphone, communication equipment. Unlike mobile phones, walkie-talkies don't have to be charged according to the call time. Comparing the cost of mobile phones and two-way walkie-talkies, users will find that walkie-talkies are more economical and practical. Handheld walkie-talkie is a kind of wireless walkie-talkie with small volume, light weight and low power consumption. Suitable for carrying or bagging, convenient for individuals to carry around and communicate with each other when traveling. Generally, its power does not exceed 5W in VHF band and 4W in UHF band. But there are also a few models whose power VHF is 6W and UHF is 5W, such as IC-T7H(VHF) is 6W. In an open area without obstacles, the communication distance can generally reach 5 kilometers. With the support of wireless communication network, the communication distance through the turntable can reach more than 10 km. This machine is suitable for close communication of mobile personnel in various occasions. In the wireless telephone series, the number and types of hand-held radios are the largest, accounting for more than 80%.

Working principle: In the transmitting part, the phase-locked loop and voltage-controlled oscillator (VCO) generate the transmitted RF carrier signal, which is buffered, amplified and amplified to generate rated RF power, filtered by the antenna low-pass filter to suppress harmonic components, and then transmitted through the antenna. Receiving part: The receiving part adopts secondary frequency conversion superheterodyne mode. The signal input from the antenna is amplified by radio frequency after passing through the transceiver conversion circuit and bandpass filter, and then enters the mixer. An amplified signal from a radio frequency is mixed with a first local oscillator signal from a PLL frequency synthesizer circuit at a first mixer to generate a first intermediate frequency signal. The first intermediate frequency signal further eliminates the clutter signals of adjacent channels through the crystal filter. The filtered first intermediate frequency signal enters the intermediate frequency processing chip and is mixed with the second local oscillator signal again to generate the second intermediate frequency signal. The second IF signal is filtered, amplified and frequency-discriminated by a ceramic filter to generate an audio signal. After amplification, band-pass filtering, de-emphasis and other circuits, the audio signal enters the volume control circuit and power amplifier for amplification, driving the speaker and getting the information people need.

Modulation signal and modulation circuit: human voice is converted into audio electrical signal through microphone, and the audio signal enters the voltage-controlled oscillator through amplification circuit, pre-emphasis circuit and bandpass filter for direct modulation. Signaling processing: the CTCSS/DTCSS signal generated by CPU is amplified and adjusted, and then enters the voltage controlled oscillator for modulation. A part of low-frequency signals obtained after receiving frequency discrimination are amplified, filtered and shaped by a sub-audio band-pass filter, and then enter the CPU, where they are compared with preset values, and the results control the output of audio power amplifiers and speakers. That is, if it is the same as the preset value, turn on the speaker; If not, please turn off the speakers.