Ham Radio General Class Practice Test

In what values are RF feed line losses usually expressed?

1. ohms per 1000 ft

2. dB per 1000 ft

3. ohms per 100 ft

4. dB per 100 ft

The correct answer is: dB per 100 ft

RF feed line losses are typically expressed in decibels (dB) per unit length, reflecting how much signal power is lost as it travels down the feed line. The decibel scale is logarithmic and is useful for representing large ranges of values, such as those experienced in RF signal loss. When specifying losses per unit length, it's common to see it indicated as dB per 100 feet, which provides a clear metric for evaluating how much signal strength diminishes over a given distance. This format allows operators to easily calculate the impact of feed line losses on their RF systems. Counting losses per 100 feet, as opposed to 1000 feet or any other measure, often aligns better with the typical lengths of feed lines used in amateur radio setups, making it more practical for operators to understand and anticipate how feed line loss may affect their transmissions. The other choices either use the wrong unit of measurement (ohms) or employ a measurement unit (1000 feet) that is less common for everyday feed line calculations in amateur radio applications.