BDS Cheat Sheet 2026

The 30 highest-yield BDS facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. What is the effect of temperature on coaxial cable signal loss? → Loss increases as temperature rises
2. What does a -6 dBmV reading indicate compared to 0 dBmV? → Signal is one-quarter the power
3. What is the typical frequency range allocated for the upstream return path in a DOCSIS 3.0 cable plant? → 5–42 MHz
4. What is the purpose of output fusing in a cable plant power supply? → To protect the coaxial plant from damage due to overcurrent conditions
5. What is the typical downstream optical power budget for a single-fiber HFC node span? → 5–10 dBm
6. What is the primary role of a voltage regulator in an HFC cable plant power supply? → To maintain a stable output voltage despite variations in utility input or connected load
7. What is the DOCSIS maximum upstream transmit power limit for a cable modem? → +58 dBmV
8. What is the primary purpose of a headend in a broadband distribution network? → To distribute content to subscribers
9. What could cause a broadband signal to weaken progressively over a distance? → Signal attenuation
10. What is the typical single-mode fiber attenuation specification at 1550 nm? → 0.2 dB/km
11. If a customer reports slow internet speeds, what should be verified first? → Signal levels at the customer’s modem
12. What is ingress noise in a cable plant? → External RF signals leaking into the cable system
13. What is the role of a Time Domain Reflectometer (TDR) in troubleshooting broadband networks? → To locate faults in the cable
14. What is a 'power hog' in the context of HFC cable plant powering? → An active device that draws significantly more current than its specification
15. What is the role of the CMTS in a DOCSIS network? → It terminates cable modem connections and bridges them to the IP network
16. What is the minimum acceptable CNR level typically required for acceptable QAM-256 signal quality in a US cable system? → 33 dB
17. What is the standard impedance of coaxial cable used in HFC distribution networks? → 75 ohms
18. When experiencing a complete loss of signal in a broadband network, what is the first step in troubleshooting? → Verify power supply to the equipment
19. What type of laser is most commonly used in HFC headends for downstream optical transmission? → DFB (Distributed Feedback) laser
20. What type of network topology is most commonly used in broadband distribution networks? → Tree topology
21. What is the function of an optical node in an HFC network? → It converts optical signals to RF signals (and vice versa) for distribution over coax
22. What is the typical AC voltage range used to power active components in an HFC outside plant? → 60-90V AC
23. Which ANSI/SCTE standard defines minimum technical requirements for cable television equipment and system performance? → ANSI/SCTE 40
24. What device is used to boost weak signals in a broadband distribution network? → Amplifier
25. What does ONU stand for in fiber access networks? → Optical Network Unit
26. What type of fiber is specified by ITU-T G.652 and is the most common fiber used in HFC networks? → Standard single-mode fiber
27. What is the maximum recommended length for a standard RG-6 subscriber drop to maintain acceptable signal levels? → 300 feet
28. Which type of splitter divides a cable signal equally between two output ports? → 2-way splitter
29. What is the standard frequency of AC power delivered by HFC cable plant power supplies in the United States? → 60 Hz
30. What is the purpose of a pad (attenuator) when installed at an amplifier input? → To reduce the input signal level to the amplifier's optimal operating range