Construction Coordinator Practice Exam

If the attenuation through a span of coaxial cable at 75 MHz is 2.5 dB, what will it be at 300 MHz?

1. 2.5 dB

2. 10.0 dB

3. 5.0 dB

4. 7.5 dB

The correct answer is: 10.0 dB

To determine the attenuation through a span of coaxial cable at a frequency of 300 MHz, we need to consider how attenuation typically scales with frequency for coaxial cables. Attenuation is usually approximated to increase linearly with frequency. If we know that the attenuation at 75 MHz is 2.5 dB, we can calculate the approximate attenuation at 300 MHz by recognizing the frequency increase from 75 MHz to 300 MHz is a factor of 4 (since 300 MHz is four times 75 MHz). When you multiply the attenuation at 75 MHz by that same factor of 4, you arrive at an estimated attenuation of 10 dB at 300 MHz: 2.5 dB * 4 = 10 dB. This reflects a common understanding in RF (radio frequency) engineering that as frequency increases, the loss (or attenuation) of signal in a coaxial cable will also increase. The linear relationship helps to provide a straightforward escalation based on frequency changes. Therefore, the attenuation at 300 MHz being 10 dB is consistent with this behavior, making it the correct answer.