1. Transmission power
Almost all walkie-talkies have high, medium and low transmit powers adjustable. For handheld two-way radios, the transmit power is generally between 0.5 and 5W; the radio can be selected between 10W and 40W. If low-power communication has obvious noise and affects communication, then switching to higher transmission power can improve communication quality and extend a certain communication distance. According to the research, as long as the transmission power is doubled, the communication distance of the walkie-talkie can be expanded to about 1.4 times of the original distance. However, if the transmission power is free to increase without any purpose, it will also bring about negative effects such as increased power consumption, increased electromagnetic radiation and increased interference.
2. Receiving sensitivity
The receiving sensitivity of the intercom has a great influence on the communication distance. When the hand-held walkie-talkie is shipped from the factory, the sensitivity has been adjusted to the best state according to the relevant technical requirements. In the absence of professional instruments and technicians, the receiving sensitivity of the walkie-talkie must not be adjusted by itself. For the user, in addition to adjusting the quiet noise value of the walkie-talkie, the receiving sensitivity of the walkie-talkie can be improved by switching to a high-gain antenna. For example, for the antenna of the handset, the drawbar gain is the highest; the r/4 whip is the second, and the spring spiral is the lowest. The outdoor gain antenna of the Taiwan machine has been clearly marked at the factory. The higher the general gain, the longer the physical size of the antenna, and the stronger the ability to receive weak signals. When switching to an antenna, you should pay attention to switching to the same frequency band antenna (the antennas in different frequency bands are not interchangeable). Otherwise, not only will the receiving sensitivity not be improved, but even a large standing wave may be generated due to the antenna mismatch, thereby damaging the RF power amplifier.
3. Choose an open place to talk
The theoretical communication distance given by the walkie-talkie manufacturers is actually tested under the barrier-free conditions in the open area. The loss of radio wave propagation is minimal in this communication environment, and the absorption of electric waves by reinforced concrete buildings in cities is more serious. A team of 3km intercoms with a nominal open area communication is often used in such buildings with a communication distance of only a few hundred meters. Therefore, when using the intercom brand indoors, you should try to choose the * window position, and outdoor use should avoid the blockage of tall buildings or trees around.
4. High antenna
The increase in antenna height is very effective for increasing the communication distance. Without increasing the transmission power, the doubling of the receiving and transmitting antennas can also increase the communication distance to about 1.4 times, which is economical and environmentally friendly. Generally, in the urban area, the outdoor communication distance is 3~5 kilometers. If one of the walkie-talkies is connected to the outdoor antenna on the top of the 5th floor, it can be connected with another outdoor walkie-talkie 20 kilometers away. The author has experimented with a pair of handhelds with an outdoor communication distance of about 4 kilometers in the urban area. One of them will be carried to the top of the mountain about 100 kilometers away from the city. The aircraft can still be connected to the intercom in the urban area. It is highly recommended that friends in the car use the car antenna. Be aware that every 3DBi gain is equivalent to doubling the transmit power of your station. At the same time, it avoids the signal shielding of your hand in the car and the radiation of the human body inside the car.
5. Communication environment and direction
Choosing the right communication environment and direction is very important, which is closely related to the quality of communication. Therefore, in general we should follow the following principles:
a) Try to choose a higher level of topographical communication. For example, if you can communicate on the second floor, don’t be on the first floor.
b) Try to choose to communicate outdoors, because the reflection and attenuation of the 70 cm wave of the building wall is very powerful.
c) Try to avoid the buildings surrounded by the buildings, the densely populated buildings in the old town, the densely populated areas, the lower floors of the high-rise buildings, the sections surrounded by large cars, the tunnels and the bridges, and the large metal billboards. .
d) Utilizing urban canyons: This is very important. We have high-rise buildings and dense buildings in our big cities. It is difficult to find real viewing distance communication opportunities, so we must make good use of the existing environment. The so-called urban canyon refers to the dry lines with dense buildings and tall buildings on both sides, and the roads are wide and narrow. Even if it is connected to the same road that intersects it (such as a vertical, oblique section), then the communication effect is generally better. On the contrary, if both sides of the link are in complicated roads or buildings, the communication effect will be very poor. Therefore, we propose that if you are going to communicate when driving, please start after driving into the wide road.
e) Choose the right direction, avoiding the occlusion of tall buildings and metal bodies between the points you are connected to. If you put it behind the direction of your communication, you can also act as a signal reflector.
f) Nighttime communication is better than daytime communication.
g) Fixed-point communication is better than mobile communication.
6. Develop good habits
Usually pay attention to check whether the battery power of the walkie-talkie is sufficient, whether the antenna connection is firm, whether the whip antenna is completely pulled out, etc. These factors directly affect the transmit power and receiving sensitivity of the walkie-talkie, and thus affect the communication distance. In addition, it is not possible to use a broken or deformed antenna. Especially for the car users, the antenna position on the roof is easy to damage the antenna during driving due to bumps or tree scraping, resulting in a significant shortening of the communication distance.