CWS CWS Basic RF Principles 2 — Questions and Answers
Question 1: A wireless signal at 5 GHz has approximately what wavelength in free space?
- 6 cm (Correct answer)
- 12 cm
- 3 cm
- 60 cm
Correct answer: 6 cm
Wavelength = speed of light / frequency; 3×10^8 / 5×10^9 ≈ 0.06 m (6 cm).
Question 2: Which RF propagation phenomenon occurs when a signal bends around the edge of an obstacle?
- Diffraction (Correct answer)
- Reflection
- Scattering
- Absorption
Correct answer: Diffraction
Diffraction is the bending of RF waves around edges or corners of obstacles.
Question 3: Converting 100 mW to dBm gives which value?
- 20 dBm (Correct answer)
- 10 dBm
- 30 dBm
- 100 dBm
Correct answer: 20 dBm
dBm = 10 × log10(100 mW / 1 mW) = 10 × log10(100) = 10 × 2 = 20 dBm.
Question 4: What effect does increasing channel width from 20 MHz to 40 MHz have on throughput and noise?
- Higher throughput and higher noise floor (Correct answer)
- Higher throughput and lower noise floor
- Lower throughput and higher noise floor
- No change in either
Correct answer: Higher throughput and higher noise floor
Doubling channel width doubles data capacity but also captures more ambient noise, raising the noise floor by ~3 dB.
Question 5: In RF terminology, what does EIRP stand for?
- Effective Isotropic Radiated Power (Correct answer)
- Equivalent Integrated RF Power
- Effective Internal Radiated Power
- Equivalent Isotropic Received Power
Correct answer: Effective Isotropic Radiated Power
EIRP is Effective Isotropic Radiated Power, representing the total power an antenna would emit if it radiated equally in all directions.
Question 6: Which type of antenna radiates RF energy equally in all directions in the horizontal plane?
- Omnidirectional (Correct answer)
- Directional
- Yagi
- Parabolic
Correct answer: Omnidirectional
Omnidirectional antennas radiate energy equally around 360° in the horizontal plane.
Question 7: Free-space path loss (FSPL) increases as frequency increases because:
- Higher-frequency signals spread over a larger effective area relative to antenna size (Correct answer)
- Higher frequencies travel faster and lose more energy
- Higher frequencies are more susceptible to absorption by oxygen
- Higher frequencies require more power to generate
Correct answer: Higher-frequency signals spread over a larger effective area relative to antenna size
FSPL increases with frequency because a fixed-size antenna captures a smaller fraction of the wavefront as wavelength decreases.
CWS CWS Basic RF Principles 2
A wireless signal at 5 GHz has approximately what wavelength in free space?