VDV Testing & Troubleshooting 5

Question 1

A technician is certifying a Cat6A cable channel and the test fails for 'alien crosstalk' (AXT). What is the most effective corrective action?

Accepted Answer

Increase physical separation between parallel cable runs or use F/UTP shielded cable

Answer

Alien crosstalk occurs between adjacent cables; increasing separation, using bundling best practices, or switching to shielded F/UTP cable are the recognized remedies.

Question 2

A technician uses a visual fault locator (VFL) on a fiber cable and sees the red laser light glowing through the jacket 2 meters from the end. What does this indicate?

Accepted Answer

A macrobend or physical damage causing light to escape the fiber at that location

Answer

A visible red glow through the fiber jacket indicates that light is escaping due to a tight bend, kink, or physical damage that disrupts total internal reflection.

Question 3

During a cable TV service call, a customer complains of a pixelating picture on all channels. The technician measures the signal level and finds it is +15 dBmV. What is the most likely problem?

Accepted Answer

The signal level is too high, causing receiver overload and distortion

Answer

Signal levels above +8 dBmV can overload cable TV receivers and cause digital pixelation or analog distortion, even though the power is high.

Question 4

A network switch port shows a link light but a laptop connected to that port cannot get an IP address. Cable certification passes. What should the technician check next?

Accepted Answer

Verify DHCP server availability and VLAN assignment on the switch port

Answer

A passing cable certification rules out physical layer issues; the inability to get an IP address with an active link points to a Layer 2/3 issue such as an incorrect VLAN, DHCP scope exhaustion, or server availability.

Question 5

A technician suspects a ground loop is causing hum bars on a video display. Which test confirms a ground potential difference between equipment?

Accepted Answer

Measure the AC voltage between the chassis grounds of the two connected devices with a multimeter

Answer

Measuring AC voltage between the chassis grounds of two devices reveals a ground potential difference, which is the root cause of hum bars induced by ground loop current.

(VDV) Voice Data Video Technician Certified Practice Test

(VDV) Voice Data Video Technician Certified Practice Test

VDV Testing & Troubleshooting 5