CWDP CWDP Antenna Design and Placement 2 — Questions and Answers
Question 1: In the US, the FCC limits maximum EIRP for point-to-multipoint 5 GHz outdoor links to which value?
- 30 dBm
- 36 dBm (Correct answer)
- 40 dBm
- 53 dBm
Correct answer: 36 dBm
The FCC limits point-to-multipoint EIRP in the 5 GHz UNII bands to 36 dBm for outdoor use.
Question 2: What is the half-power beamwidth (HPBW) of an antenna?
- The angle at which the antenna gain drops to 3 dB below peak (Correct answer)
- The total angle covered by the antenna pattern
- The angle between the two nulls in the radiation pattern
- The beamwidth at which interference is eliminated
Correct answer: The angle at which the antenna gain drops to 3 dB below peak
HPBW is the angular width measured between the two points where gain falls to half (-3 dB) of its maximum value.
Question 3: A designer wants to mount antennas in the ceiling of a 10,000 sq ft warehouse. What spacing consideration is most critical?
- Keeping antennas at least 50 ft apart to avoid interference
- Ensuring overlap of approximately 15–20% between cell edges (Correct answer)
- Placing antennas only at perimeter walls
- Avoiding any overlap to maximize channel reuse
Correct answer: Ensuring overlap of approximately 15–20% between cell edges
A 15–20% cell-edge overlap ensures seamless roaming and prevents coverage gaps in large open spaces.
Question 4: Which cable type is preferred for short indoor antenna runs to minimize insertion loss?
- RG-58
- RG-8
- LMR-400 (Correct answer)
- Cat6 coax
Correct answer: LMR-400
LMR-400 has lower attenuation per foot than RG-58 or RG-8, making it preferred for minimizing cable losses.
Question 5: What effect does each 3 dB increase in antenna gain have on the effective coverage radius (assuming free-space path loss)?
- Doubles the coverage radius
- Increases radius by approximately 41% (Correct answer)
- Triples the coverage radius
- Has no effect on coverage radius
Correct answer: Increases radius by approximately 41%
A 3 dB gain increase doubles the power density, which increases the free-space coverage radius by roughly 41%.
Question 6: Which antenna characteristic describes its ability to reject interference from directions outside its main lobe?
- Front-to-back ratio (Correct answer)
- Beamwidth
- Polarization diversity
- Gain compression
Correct answer: Front-to-back ratio
The front-to-back ratio indicates how much more gain an antenna has in its main direction versus the opposite direction.
CWDP CWDP Antenna Design and Placement 2
In the US, the FCC limits maximum EIRP for point-to-multipoint 5 GHz outdoor links to which value?