VDV Testing & Troubleshooting 4

Question 1

A technician is using a time domain reflectometer (TDR) on a coaxial cable and the display shows a positive reflection spike. What does a positive reflection indicate?

Accepted Answer

An open circuit or high-impedance fault

Answer

A positive reflection on a TDR trace indicates an open circuit or impedance higher than the cable's characteristic impedance, such as a missing terminator.

Question 2

Which fiber optic test is used to verify the end-to-end optical loss budget of a newly installed link before connecting active equipment?

Accepted Answer

Optical loss test using a light source and power meter (insertion loss test)

Answer

An insertion loss test using a calibrated light source and optical power meter directly measures the total end-to-end attenuation against the system's loss budget.

Question 3

A BNC connector on a 75-ohm coaxial cable shows 50 ohms impedance on a TDR. What is the most likely problem?

Accepted Answer

A 50-ohm BNC connector was mistakenly installed instead of a 75-ohm connector

Answer

50-ohm and 75-ohm BNC connectors are physically compatible but electrically mismatched; using a 50-ohm connector on 75-ohm cable creates a measurable impedance discontinuity.

Question 4

During troubleshooting, a technician discovers that a Cat5e cable run passes all wire map tests but fails the Power Sum ELFEXT (PS-ELFEXT) test. What does this failure indicate?

Accepted Answer

Excessive far-end crosstalk which degrades signals at the distant end of the cable

Answer

PS-ELFEXT measures power sum equal-level far-end crosstalk; a failure indicates the cable or terminations are coupling noise onto pairs at the far end, impairing high-speed data transmission.

Question 5

A technician notices that a wireless access point connected to a PoE switch port does not power on. After confirming the AP supports PoE, what is the NEXT step?

Accepted Answer

Test the patch cable with a cable tester and verify the switch port PoE output with a PoE tester

Answer

A faulty patch cable or a non-functional switch PoE port are common causes; verifying the cable and measuring the PoE output isolates the fault before replacing equipment.

(VDV) Voice Data Video Technician Certified Practice Test

(VDV) Voice Data Video Technician Certified Practice Test

VDV Testing & Troubleshooting 4