150MHz and 400MHz walkie-talkies have a slightly longer talking distance in urban areas because the antenna gain is higher than that of 150MHz machines. In mountainous areas, the long communication distance of 150MHz walkie-talkie is due to the existence of electric wave diffraction. Functionally, both walkie-talkies are similar.
2. Different receiving ranges: the range of the high segment is about 440/450-470, and the range of the low segment is about 400-430/450, so the receiving ranges are different. Nowadays, many walkie-talkies have full-range radios, covering the range of 400-470.
3. The frequencies are different, one is high frequency and the other is low frequency.
Extended data:
Working principle of walkie-talkie:
1. transmitting part: the transmitted RF carrier signal is generated by a phase-locked loop and a voltage-controlled oscillator (VCO), and the rated RF power is generated by buffer amplification and excitation amplification, filtered by an antenna low-pass filter to suppress harmonic components, and then transmitted through an antenna.
2. Receiving part: The receiving part mixes the amplified signal from the radio frequency with the first local oscillator signal from the PLL frequency synthesizer circuit at the first mixer to generate a first intermediate frequency signal. The first intermediate frequency signal further eliminates the clutter signals of adjacent channels through a 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.
3. Modulation signal and modulation circuit: human voice is converted into audio electrical signal through microphone.
4. Signaling processing: The CTCSS/CDCSS 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 the audio power amplifier and speakers. That is, if it is the same as the preset value, turn on the speaker; If not, please turn off the speakers.