VDV Video Distribution 2 — Questions and Answers
Question 1: What is the primary purpose of a distribution amplifier (DA) in a video system?
- Convert analog video to digital
- Split and amplify one signal to multiple outputs without degradation (Correct answer)
- Reduce video bandwidth to save cable
- Convert composite video to component video
Correct answer: Split and amplify one signal to multiple outputs without degradation
A distribution amplifier splits one input signal into multiple isolated outputs while restoring signal strength to compensate for split losses.
Question 2: Which impedance is standard for coaxial video cable used in CCTV and broadcast distribution?
- 50 ohms
- 75 ohms (Correct answer)
- 100 ohms
- 120 ohms
Correct answer: 75 ohms
75-ohm coaxial cable is the industry standard for video distribution because it minimizes signal loss at video frequencies.
Question 3: A video signal loses approximately how much level for each 100 feet of RG-59 cable at 3.58 MHz?
- 1 dB
- 2 dB
- 4 dB (Correct answer)
- 10 dB
Correct answer: 4 dB
RG-59 coaxial cable has approximately 4 dB of loss per 100 feet at the color subcarrier frequency of 3.58 MHz.
Question 4: In a star topology video distribution system, what is the main component at the center?
- Passive splitter
- Distribution amplifier or matrix switcher (Correct answer)
- Balun transformer
- Termination block
Correct answer: Distribution amplifier or matrix switcher
Star topologies use a central distribution amplifier or matrix switcher to feed each endpoint individually, ensuring equal signal levels.
Question 5: What is the correct termination for an unused output port on a passive video splitter?
- Leave it open
- Short it to ground
- Install a 75-ohm terminator (Correct answer)
- Install a 50-ohm terminator
Correct answer: Install a 75-ohm terminator
Unterminated ports cause reflections and standing waves; a 75-ohm terminator absorbs the signal and prevents impedance mismatches.
Question 6: Which type of cable is preferred over RG-59 for long video distribution runs due to lower loss?
- RG-6 (Correct answer)
- RG-58
- RG-174
- RG-8
Correct answer: RG-6
RG-6 has a larger center conductor and better shielding than RG-59, resulting in approximately 30% lower attenuation over long distances.
Question 7: When cascading multiple distribution amplifiers, what problem can accumulate and degrade picture quality?
- Impedance buildup
- Noise and distortion (Correct answer)
- Reduced bandwidth
- Increased DC offset
Correct answer: Noise and distortion
Each active amplifier stage adds noise and harmonic distortion; cascading too many DAs compounds these impairments and degrades SNR.
VDV Video Distribution 2
What is the primary purpose of a distribution amplifier (DA) in a video system?