Today, let's talk about the hand-held group walkie talkie
Let's start with the traditional walkie talkie. First, the civil analog walkie talkie is characterized by its simplicity, ease of use and low cost; Secondly, the digital walkie talkie is also called DMR walkie talkie. The civil digital walkie talkie integrated with modern communication technologies such as digital FM has strong anti-interference ability, clear voice, easy encryption and other characteristics, and can also provide additional services such as SMS and relative positioning; Then, DMR digital analog integrated interphone is derived. The power of this kind of traditional walkie talkie depends on the wattage. Generally speaking, the greater the power, the farther it will go. Of course, it depends on the environment. The grid and people will absorb the signal. Another way is to look at the frequency band. The U band is suitable for urban use. The commonly used frequency band is 400-470MHz; Segment V is suitable for open field and offshore operations, and the commonly used frequency band is 136-174MHz; There is also a 350MHz police PDT interphone frequency band. Because the electromagnetic wave length of the frequency band is short, the displacement between wave peaks is narrow, the diffraction ability is weak, and the penetrability is strong. In short, the greater the number of frequency bands, the stronger the penetration, the shorter the distance, and the smaller the number of frequency bands.
In recent years, with the development of 4G and 5G Internet access technology of mobile Internet, public network cluster intercom (also known as POC intercom and network intercom) has emerged. Its advantage is that there is no distance limit, and it can also expand the cluster functions such as positioning, video echo, information management, but its disadvantage is also obvious. It requires a network, both WAN and LAN; This kind of walkie talkie is generally based on the Android system, which needs to be implemented by installing corresponding software. There are a lot of such software, but they cannot be interconnected. Even though the gateway transit is used to solve the problem of intercommunication, it is still a mobile phone solution after all. For ordinary civil walkie talkies, the price is still slightly higher, so the CAT1 public network walkie talkie is derived. The bandwidth of CAT1 is sufficient to support voice transmission and the cost is low, As a result, the walkie talkies are popular with many manufacturers. Therefore, the walkie talkies are generally small screen or no screen to maximize the price.
Then the problem arises again. Traditional walkie talkies have distance limitations, and public network walkie talkies must have signals. Is it feasible to combine the two? At this time, the wide and narrow band integration terminal came out, also known as public network+DMR digital analog integrated cluster interphone, which is simply mobile phone+traditional interphone+public network interphone. What you can see on the market is 1W 2W 4W. 1W is not necessary to have it. The actual measurement in cities is only 1km, 2W is higher, 2-3 km, but it is more professional at 4W. There are certain requirements for battery, circuit board design and software. In the absence of network, intercom, SMS, positioning and other functions can be realized at an effective distance;
How to communicate when there is no signal, far distance and no relay, such as emergency rescue and Gobi Forest? Tiantong satellite phone is here to help you! Operators can directly apply for Tiantong card, and the price is not expensive. It is 100 meters / month, 60 minutes, 1.6/minute of voice outside the package, and 0.4/piece of SMS. Now there is an enhanced version of the third mock examination, mobile phone + traditional walkie talkie + public network walkie talkie + satellite phone, sea, land and air!