SBCA System Maintenance 2 — Questions and Answers
Question 1: What is the primary purpose of performing a spectrum analyzer sweep during satellite system maintenance?
- To measure signal-to-noise ratio only
- To identify interference, spurious signals, and verify transponder cleanliness (Correct answer)
- To calibrate the LNB gain
- To measure dish azimuth alignment
Correct answer: To identify interference, spurious signals, and verify transponder cleanliness
Spectrum analyzer sweeps reveal interference sources, spurious emissions, and verify that the transponder bandwidth is clean before and after maintenance.
Question 2: Which condition most commonly causes an IRD (Integrated Receiver/Decoder) to display a 'No Signal' error after a thunderstorm?
- Software corruption in the IRD
- Water ingress or physical damage to the LNB or feedhorn (Correct answer)
- Expired conditional access card
- Incorrect DiSEqC switch position
Correct answer: Water ingress or physical damage to the LNB or feedhorn
Thunderstorms can cause water ingress into the feedhorn or LNB, leading to signal blockage or component failure and a resulting 'No Signal' error.
Question 3: When verifying EIRP (Effective Isotropic Radiated Power) at a receive site, which tool provides the most accurate field measurement?
- A standard voltmeter
- A calibrated spectrum analyzer with a known-gain antenna (Correct answer)
- A TDR (Time Domain Reflectometer)
- A digital multimeter
Correct answer: A calibrated spectrum analyzer with a known-gain antenna
A calibrated spectrum analyzer paired with an antenna of known gain allows technicians to calculate actual received EIRP from measured signal levels.
Question 4: What does an elevated noise floor on a spectrum analyzer indicate in a satellite receive system?
- Strong signal reception
- Possible LNB saturation or interference entering the system (Correct answer)
- Correct LO (local oscillator) frequency
- Proper cable impedance matching
Correct answer: Possible LNB saturation or interference entering the system
An elevated noise floor suggests interference, LNB saturation, or a noisy component is degrading the system's noise performance.
Question 5: During preventive maintenance, a technician finds corrosion on the N-type connector of a cable feeding an LNB. What is the correct remediation step?
- Apply electrical tape over the connector
- Clean with contact cleaner, re-terminate with a new weatherproofed connector (Correct answer)
- Increase transmit power to compensate
- Replace only the LNB
Correct answer: Clean with contact cleaner, re-terminate with a new weatherproofed connector
Corroded connectors must be re-terminated with a new connector sealed with weatherproofing compound to restore signal integrity and prevent recurrence.
Question 6: What is the recommended interval for re-torquing dish mount bolts in a high-wind environment?
- Every 5 years
- Every 6–12 months or after severe weather events (Correct answer)
- Only at initial installation
- Every 10 years
Correct answer: Every 6–12 months or after severe weather events
In high-wind environments, mount hardware can loosen over time; re-torquing every 6–12 months or after severe weather prevents pointing drift.
Question 7: A VSAT system experiences intermittent outages only during afternoon hours. What is the most likely cause?
- IRD firmware bug
- Sun outage (solar interference) as the sun transits behind the satellite (Correct answer)
- Cable corrosion
- Incorrect symbol rate setting
Correct answer: Sun outage (solar interference) as the sun transits behind the satellite
Sun outages occur predictably when the sun passes through the antenna's beam path, causing high noise temperatures and signal degradation during specific times.
SBCA System Maintenance 2
What is the primary purpose of performing a spectrum analyzer sweep during satellite system maintenance?