The authors use computer simulation and experiment to study thermal characteristics of a less expensive design of the air cooling system for transmit/receive modules based on the heat sink with the dimensions of 25 × 324 × 500 mm made of mass-produced heat sink profile. The total power of the 8 transistors in the transmit/receive module is 224 W. It is shown that the increase in air velocity in the heat sink channels from 1 to 30 m/s causes an approximately twofold drop in the maximum temperature of the mounting surface (from 78.45 to 38.70 °C) and a decrease in thermal resistance of the cooling system by 3.16 (from 0.262 to 0.083 °C/W). The air velocity range from 5 to 10 m/s proves to be the most rational option. For the inlet air temperature of 20 °C, the temperature in the spots where the transistors are mounted remains below 56.3 °C for the air velocity of 5.5 m/s in the heat sink channels and below 51.8 °C for 10.5 m/s. A new original technical solution based on low-cost flat gravity heat pipes with a threaded evaporator will provide the efficiency of the cooling system at higher inlet air temperatures.