There are many kinds of walkie-talkies, so how to choose them is very important. Walkie-talkies are divided into two categories: professional machines and civil machines. Professional machines refer to machines with emission power greater than 4W. At present, the most common professional machines on the market are those with the transmission power of 4W and 5W, such as Motorola, Jianwu, vitesse, Aikemu and so on. The actual communication distance of this walkie-talkie is generally between 0- 10 km, and it is mainly used in applications that need a long communication distance, such as public security, security, professional mountaineers and so on. The price of this kind of machine is relatively high, generally between 1000-2000. Commonly used interphones with moderate prices are: Motorola GP2000/s, Jianwu TK-3207TK-32 17, vitesse VX- 168VX-4 18, and Ike Muic -F26.
Civil walkie-talkie refers to the machine whose transmitting power does not exceed 0.5W At present, the more common civil machines on the market are Motorola and Southern Bell. The actual calling distance of this walkie-talkie is generally between 0 and 3 kilometers, and it is mainly used in applications where the calling distance is not high, such as restaurants, small parties, exhibitions, outings and so on. The price of this machine is relatively low, generally between 240-600. Our similar products are: Motorola T5728.
What factors affect the communication distance and effect of interphone?
The factors affecting the communication distance and effect of walkie-talkie are as follows:
1, system parameter
(1) The stronger the output power of the transmitter, the larger the coverage of the transmitted signal and the farther the communication distance. However, the transmission power should not be too large, which not only consumes power and affects the life of power amplifier components, but also has strong interference, which affects the communication effect of others and will also produce radiation pollution. Radio regulatory agencies in various countries have clear regulations on the transmission power of communication equipment.
(2) The higher the receiving sensitivity of the communication machine, the farther the communication distance.
(3) the gain of the antenna. When the antenna is matched with the machine, the height of the antenna is usually increased and the receiving or transmitting ability is enhanced. The antenna used in hand-held walkie-talkies is generally a spiral antenna, which has smaller bandwidth and gain than other kinds of antennas and is more easily influenced by human body.
2. Environmental factors
Environmental factors mainly include path, tree density, electromagnetic interference of environment, buildings, weather conditions and terrain differences. These factors and other parameters directly affect the signal field strength and coverage.
3. Other influencing factors
(1) The battery is low. When the battery is low, the call quality will deteriorate. In severe cases, there will be noise, which will affect the normal call.
(2) Antenna matching. The antenna frequency band is inconsistent with the machine frequency band, and the antenna impedance does not match, which will seriously affect the call distance. For users, pay attention to tighten the antenna when switching to the walkie-talkie antenna. In addition, you can't use the antenna provided by the manufacturer casually, and you can't use the antenna that doesn't meet the machine frequency.
4. Sound quality is good or bad
It mainly relies on pre-emphasis and de-emphasis circuits, as well as advanced speech processing circuits "the application of speech companding circuit and low-level expansion circuit", which has a good effect on fidelity speech.
Explanation of walkie-talkie function terms
1. Monitor
A monitoring method for receiving weak signals. By pressing the special key to forcibly connect the receiving signal channel, the operator can distinguish the weak sound in the speaker with his ears and achieve the purpose of listening.
Step 2 scan
A listening mode for listening to all channels.
By pressing the dedicated key, the receiving circuit can receive the signals in the channels one by one in a certain order for a period of time. If the receiving time of each channel is 100ms, ten channels can be scanned every second, that is, the scanning speed is10 ch/s.
3. Priority channel scanning function (priority channel scanning)
In the scanning process, the set priority channels are preferentially scanned.
4. Delete/add scanning channels.
Delete or add channels in the scan list.
5. Voice control (VOX)
When this function is activated, the transmission operation can be started directly by voice without pressing PTT key.
6. Start the time-limited function (TOT: Timeout Timer)
This function is used to limit the user's overtime transmission on a channel, and at the same time avoid the damage to the walkie-talkie caused by long-term transmission.
7. Power saving function (battery saving)
In order to save electricity and prolong standby time, the walkie-talkie will save electricity without receiving transmission and pressing the button for a period of time, and will be turned off and on for a period of time. The switching duration ratio is about 1: 4. When receiving the signal or operating the key, the interphone immediately exits the power-saving state and enters the normal state.
8. High/low power selection function (high/low power)
This function allows users to choose high power or low power according to the actual situation.
9. Hair prohibition function (busy channel locking)
When using this function, users are prohibited from transmitting signals on busy channels.
10. squelch level
The intensity of noise in the received signal corresponds to the intensity of the signal, and the stronger the signal, the weaker the noise. The maximum noise and the minimum noise are divided into several levels, and each level is called the first level. The number of divided files is called squelch series. Users can choose according to the actual situation.
1 1.CTCSS/CDCSS function
Use this function to avoid receiving irrelevant calls.
12. Dual-tone/Dual-tone multi-frequency selective calling function
Use dual tone or DTMF signal to select and call the corresponding interphone.
13. Reverse frequency function (reverse frequency)
When using the scrambling function, the transmitting frequency and receiving frequency of interphone will be interchanged, and the set signaling will also be interchanged.
14. Intercom function
When offline function is used, the transmitting frequency of interphone becomes the same as the receiving frequency; The transmission signaling is also changed to be the same as the reception signaling.
15. Automatic cross-pool.
When the intercom receives a correctly coded call, it will send a signal to the caller to respond to the call.
16. Emergency alert
Press the special alarm key, and the intercom will give an alarm sound at the maximum sound or send a predetermined alarm code to other mobile phones or base stations.
17. Patrol record
When the patrol personnel arrive at the patrol point, the walkie-talkie will receive the inquiry signal sent by the patrol register, and then automatically start the registration operation, and send its own identity code and other information to the patrol register for registration, indicating that the patrol personnel have arrived there.
18. Key lock function (key lock)
Use this function to prevent key misoperation.
19. Battery indicator
Displays the battery charge.
20. Lighting function (backlight)
Used for operation at night or in dim light, with clear LCD screen and buttons.
2 1. Replication function (cloning)
This function allows the data in one walkie-talkie to be copied to other walkie-talkies of the same model.
22. adjustment; adjust
The variation of carrier parameters is controlled by one or several parameters of the modulation signal. According to different control parameters, modulation can be divided into amplitude modulation, frequency modulation and phase modulation.
audio frequency
Audio refers to the frequency of human voice, usually refers to the frequency band of 300Hz-3400Hz.
24. Carrier wave
Voice, digital signals, signaling and other useful signal carriers are easy to transmit high-frequency electromagnetic waves.
25. Channel and channel spacing
Channel refers to the frequency value occupied when transmitting and receiving. The frequency difference between adjacent channels is called channel interval. The specified channel intervals are 25KHz (broadband), 20KHz, 12.5KHz (narrowband), etc.
26. Two tones
Two-tone, two-tone signaling, consisting of two audio signals, A+B. Pronounce a for a while and b for a while. With dual tone signal, you can choose to call the corresponding interphone.
27. Five tones
5-tone, 5-tone signaling has the same function as dual-tone signaling, except that it consists of five frequencies.
28.CTCSS
CTCSS (continuous tone controlled squelching system) and continuous voice controlled squelching system, commonly known as sub-audio, is a technology of adding frequencies lower than audio (67Hz-250.3Hz) to audio signals and transmitting them together. Because its frequency range is lower than the standard audio, it is called secondary audio. After the interphone demodulates the received intermediate frequency signal, it filters and shapes the secondary audio signal, and then inputs it into the CPU, and compares it with the CTCSS frequency set by this machine, so as to decide whether to turn on the mute.
29.CDCSS
Cdcss (continuous digital control silencing system) is a kind of continuous digital control silencing system, which has the same function as CTCSS, but the difference is that it uses digital coding as the condition of whether the silencing is turned on or not.
30. Dual tone multi-frequency
DTMF (Dual Tone Multifrequency) is composed of a high-frequency group and a low-frequency group, and each group contains four frequencies. A high frequency signal and a low frequency signal are superimposed to form a combined signal, which represents a number. DTMF signaling has 16 codes. Using DTMF signaling, you can choose to call the corresponding interphone.