ARRL Technician Practice Exam

Why is it important to have a low SWR in an antenna system that uses coaxial cable feed line?

1. To allow for easier connection

2. To protect the antenna from damage

3. To allow the efficient transfer of power and reduce losses

4. To increase the range of the antenna

The correct answer is: To allow the efficient transfer of power and reduce losses

Having a low Standing Wave Ratio (SWR) in an antenna system is crucial because it facilitates the efficient transfer of power from the transmitter through the coaxial cable to the antenna. When the SWR is low, it indicates that the impedance of the antenna is closely matched to the impedance of the feed line, typically 50 ohms for most coaxial cables. This matching minimizes the amount of reflected power, ensuring that most of the transmitted power is radiated by the antenna rather than being reflected back towards the transmitter. High SWR can lead to several issues, such as increased losses in the feed line due to the reflected power, which can generate heat and potentially damage both the transmitter and the coaxial cable over time. Therefore, maintaining a low SWR is essential for optimizing performance and ensuring the system operates efficiently, allowing for maximum signal strength and effective communication. Other options, while they touch on elements of antenna systems, do not directly address the primary reason for maintaining low SWR. For instance, while protecting the antenna from damage is a valid concern, it is a secondary result of ensuring a low SWR rather than the main purpose. Thus, efficient power transfer and loss reduction is the fundamental reason for aiming for a low SWR in