What happens as the frequency of a signal in coaxial cable is increased?

• A. The signal loss decreases
• B. The signal is amplified
• C. The loss increases
• D. The capacitance increases

Answer: (C)

As the frequency of a signal transmitted through coaxial cable increases, the loss in the cable also increases. This phenomenon can be attributed to several factors. First, coaxial cables have inherent resistive losses that are affected by the frequency; as frequency rises, the skin effect—where alternating current (AC) flows near the surface of the conductor—becomes more pronounced. This effectively reduces the effective area through which the current can flow, leading to higher resistance and therefore, increased losses.

Additionally, at higher frequencies, there are other forms of transmission line losses that come into play, such as dielectric losses in the insulating material surrounding the conductors and radiation losses from the cable itself. These combine to contribute to the overall increase in signal loss as the frequency goes up.

Understanding this behavior is crucial for ham radio operators, especially when designing and implementing RF systems, as it affects the selection of coaxial cables based on the operating frequency range to minimize loss and ensure efficient signal transmission.