ARRL Technician Practice Exam

What is the approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power?

1. 1.5 to 1

2. 2 to 1

3. 3 to 1

4. 4 to 1

The correct answer is: 2 to 1

The approximate SWR (Standing Wave Ratio) value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power is typically around 2 to 1. At this SWR level, the transmitter detects that the amount of reflected power is increasing significantly, indicating that the load (such as an antenna) may not be properly matched to the transmitter output. When the SWR rises above this threshold, it could lead to excessive heat generation and potential damage to the transmitter components due to the high levels of reflected power. As a protective measure, many transmitters are designed to automatically reduce their output power to safeguard against damage caused by these unfavorable conditions. Understanding this aspect is crucial for amateur radio operators, as maintaining an appropriate SWR is essential for efficient operation and to prevent damage to their equipment. The specified threshold of 2 to 1 reflects a balance between allowing good performance while still providing a safeguard for the transmitter.