CWS Basic RF Principles Questions and Answers — Questions and Answers
Question 1: An RF signal travels between a transmitter and receiver. As it propagates through the air, it encounters a large, smooth metal-paneled building. Which of the following RF behaviors is MOST likely to occur?
- Absorption
- Diffraction
- Reflection (Correct answer)
- Scattering
Correct answer: Reflection
Reflection occurs when an RF wave strikes a smooth surface that is large relative to the wavelength of the signal. A metal-paneled building is a prime example of such a surface, causing the signal to bounce off.
Question 2: A network technician is setting up a point-to-point wireless bridge between two buildings. To ensure a reliable link, they must account for the area around the visual line of sight that needs to be clear of obstructions. What is this area called?
- The Azimuth Plane
- The Fresnel Zone (Correct answer)
- The Radiation Pattern
- The Beamwidth Area
Correct answer: The Fresnel Zone
The Fresnel Zone is an elliptical area immediately surrounding the visual path of an RF link. For optimal performance, especially in point-to-point links, it's recommended that at least 60% of the first Fresnel Zone be clear of obstructions to avoid signal degradation.
Question 3: Which of the following units of measurement represents an absolute power level referenced to 1 milliwatt?
- dBi
- dB
- dBd
- dBm (Correct answer)
Correct answer: dBm
dBm stands for 'decibels relative to 1 milliwatt'. It is an absolute unit of power, where 0 dBm is equal to 1 mW. dBi and dBd are relative gain values compared to isotropic or dipole antennas respectively, and dB is a relative ratio between two values.
Question 4: A wireless engineer notices that as the frequency of an RF signal increases, its wavelength __________.
- increases
- remains the same
- decreases (Correct answer)
- becomes unstable
Correct answer: decreases
Frequency and wavelength are inversely proportional. As the frequency (the number of cycles per second) of an RF signal increases, the physical distance of each wave (the wavelength) becomes shorter.
Question 5: What does a Voltage Standing Wave Ratio (VSWR) of 1:1 on an antenna system signify?
- A complete signal reflection back to the transmitter.
- The antenna is operating on the wrong frequency.
- A perfect impedance match between the transmitter, cable, and antenna. (Correct answer)
- Maximum possible antenna gain is being achieved.
Correct answer: A perfect impedance match between the transmitter, cable, and antenna.
A VSWR of 1:1 indicates a perfect impedance match, meaning all the power from the transmitter is being radiated by the antenna with no power being reflected back. This is the ideal, though often unachievable, state for maximum power transfer efficiency.
Question 6: An 802.11ac signal operating in the 5 GHz band will experience more of what compared to an 802.11g signal in the 2.4 GHz band, assuming both are transmitted at the same power over the same distance in free space?
- Refraction
- Free Space Path Loss (FSPL) (Correct answer)
- Phase shifting
- Multipath propagation
Correct answer: Free Space Path Loss (FSPL)
Free Space Path Loss (FSPL) is greater at higher frequencies. As RF signals propagate, they lose strength over distance. This loss is proportional to the square of the frequency. Therefore, a 5 GHz signal will attenuate more over the same distance than a 2.4 GHz signal.
CWS Basic RF Principles Questions and Answers
An RF signal travels between a transmitter and receiver.
As it propagates through the air, it encounters a large, smooth metal-paneled building.
Which of the following RF behaviors is MOST likely to occur?