ARRL Technician Practice Exam

What could potentially cause erratic changes in SWR readings?

1. A mismatch in impedance

2. A loose connection in an antenna or a feed line

3. Excessive signal strength

4. Higher frequency operation

The correct answer is: A loose connection in an antenna or a feed line

Erratic changes in SWR (Standing Wave Ratio) readings can often be linked to physical issues in the antenna system, such as a loose connection. When there is a loose connection in an antenna or a feed line, it disrupts the stability of the signal flow, leading to inconsistent reflections of the RF energy back towards the transmitter. This inconsistency will manifest as erratic or fluctuating SWR readings on the meter because the SWR is highly sensitive to changes in the quality of the connection points along the feed line. The other options can cause SWR issues but in more stable or predictable manners. For instance, while a mismatch in impedance will lead to a high SWR reading, it generally doesn’t result in erratic changes but rather a steady reading that reflects that mismatch. Similarly, excessive signal strength might lead to signal distortion or overload but isn’t typically responsible for erratic SWR. Higher frequency operation could have an effect on the SWR, but it would generally create a consistent shift rather than erratic fluctuations. Therefore, a loose connection stands out as the primary cause of erratic changes in SWR readings.