Mobile radio is routinely necessary radio equipment for hams. Compared with handheld walkie-talkies, the mobile radio with high power. The high power increases the possibility of the power amplifier burning out. It is common for high-power car walkie-talkies.
Why does the mobile radio burn the power amplifier?
In fact, this is not an unexpected phenomenon. When radiofrequency current passes through a conductor, electromagnetic waves are generated. The power amplifier in the mobile radio sends this radiofrequency current to the antenna. When the impedance of the feeder and the antenna match, the radiofrequency current energy is all radiated by the antenna at this time, and there is no energy reflection loss. At this time, the standing wave ratio is an ideal value of 1. When the standing wave ratio is infinite, it means total reflection and energy is not emitted. At this time, the reflected energy causes the temperature of the power amplifier module to rise until it burns out.
"If the antenna feed is not well-matched, it will burn the power amplifier." That is, if the standing wave ratio is high, there will be the risk of burning the power amplifier. In addition, many power amplifiers have been burnt due to this. For this reason, almost all mobile radio packages, manuals, or fuselages reminded: Antennas must be installed before transmitting!
As many users do not pay much attention to antennas and feeders and do not understand the concept of standing wave ratio, they think that everything will be fine after installing a good vehicle station, but they do not know the importance of antennas and feeders to the entire vehicle station system. Choosing a poor-quality antenna feeder, or using unscientific installation methods, caused the standing wave to be high, which caused the vehicle-mounted station power amplifier to burn out.
The power amplifier of the vehicle-mounted station is burned out. Replacing a power amplifier module is not as simple as replacing the chip. You need to disassemble the entire circuit board and match the tank circuit. After the replacement, it must be tested and adjusted through comprehensive testing and other equipment. All indicators can be used after meeting the requirements.
Therefore, when the vehicle-mounted radio is transmitting, especially when transmitting with high power, be sure to connect a matching antenna.