If signal interworking is to be realized, the following conditions need to be met:
1, must have the same frequency.
The premise of intercommunication between walkie-talkies is that the communication frequencies set between walkie-talkies should be modulated to the same. Different brands of walkie-talkies may have the same frequency band. After writing the walkie-talkies with the same frequency through frequency writing software, they can communicate with each other. If the frequency bands are different, it depends on whether the walkie-talkie is in the same frequency band. If there are the same frequency bands, you can also talk back and forth by setting the same frequency value.
2. Within the signal coverage range
Only when we can receive the signal can we communicate. If it is not in the signal coverage range, even if the frequency is adjusted to the same, it is impossible to communicate. If the signal is insufficient, the signal may be better by using a high-gain antenna or standing at a higher place or adding relay stations.
3, the same consonant
In order to prevent useless signal interference, sometimes the walkie-talkie will be set with receiving consonants. When the sub-tone of the wireless signal sent by another walkie-talkie is different from the receiving sub-tone, the walkie-talkies will not be able to communicate with each other.
4. Same system, key or ID
Some walkie-talkies, such as digital walkie-talkies, will set a security key or ID for communication security. Only the keys or ids of both ends are consistent can they be used. This is a situation that cannot be ignored, and often everyone ignores this problem.
As long as different walkie-talkie brands meet the above four points at the same time, they can communicate with each other and realize the intercom function.
The working principle of walkie-talkie is as follows:
1, transmission part:
A phase-locked loop (PLL) and a voltage-controlled oscillator (VCO) generate a transmitting RF carrier signal, which is buffered, amplified and amplified to generate rated RF power, and harmonic components are suppressed by an antenna low-pass filter, and then transmitted by an antenna.
2. Receiving part:
The receiving part mixes an amplified signal from a radio frequency with a first local oscillator signal from a PLL frequency synthesizer circuit at a first mixer, and generates 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.
3, modulation signal and modulation circuit:
The human voice is converted into audio electrical signals through a 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.
References:
Baidu encyclopedia intercom