Handheld radio

Armed with interphone, used communication equipment. 2 way radio is different from mobile phones, it need not according to call time billing. More mobile phones and two-way radios cost, users will find more economical and practical intercom.
The working principle of handheld radio:
1.launch part:
Phase lock loop and voltage control oscillation (VCO) produce launch rf carrier signal, after buffer amplifier, driver amplification, amplifiers, produce rated rf power, after antenna low-pass filter, suppress harmonic composition, and then through the antenna launch out.
2, receiving part:
Receiving part to second frequency conversion specialized superheterodyne way, from the input signal after sending and receiving antenna transform circuit and band pass filter rf after amplification, after band pass filter and into a frequency mixing, will come from rf signal from the amplification and phase lock loop of the circuit frequency synthesizer vibration signal of the first ,in the first mixers place frequency mixing and produce the first intermediate frequency signal. The first intermediate frequency signal through the crystal filter to further eliminate clutter signal of adjacent to the word. After the first intermediate frequency signal of the filter into the intermediate frequency processing chip, and the second this vibration signal frequency mixing generation again the second intermediate frequency signal, the second intermediate frequency signal through a ceramic filters filter out useless stray signals, be amplified and popularly used, produce the audio signal.
3,modulation signal and modulation circuit:
The voice through the microphone converts audio electrical signal, audio signal through the amplifier circuit, the aggravating circuit and band pass filter into the vco directly modulation.
4.signal processing:
CPU produce CTCSS/DTCSS signal amplified adjustment, into the vco for modulation. After receiving is popularly used get low frequency signal, and part of the amplified and the audio band pass filter for filter plastic, into the CPU, and the value is used in the comparison, will the results control the output of the audio power amplifier and speakers.