AET Communication Systems 2

Question 1

What VSWR reading indicates a perfect impedance match between a VHF comm transmitter and its antenna?

Accepted Answer

1:1

Answer

A 1:1 VSWR means no power is reflected, so the load matches the line impedance exactly.

Question 2

An antenna system shows a VSWR of 3:1. Approximately what percentage of forward power is reflected?

Accepted Answer

25%

Answer

Reflection coefficient = (3-1)/(3+1) = 0.5, and reflected power = 0.5² = 25%.

Question 3

Which piece of test equipment should be connected to a transmitter's output instead of the antenna when testing power on the bench to avoid radiating a signal?

Accepted Answer

Dummy load

Answer

A dummy load is a non-radiating 50-ohm resistive load that absorbs transmitter power safely.

Question 4

What is the characteristic impedance of the coaxial cable normally used for aircraft VHF communication antennas?

Accepted Answer

50 ohms

Answer

Aircraft RF systems such as VHF comm use 50-ohm coax like RG-58 or RG-400.

Question 5

A technician suspects a break somewhere along a long coax run in the fuselage. Which instrument best locates the fault distance?

Accepted Answer

Time-domain reflectometer

Answer

A TDR sends a pulse down the cable and times the reflection to pinpoint the fault's distance.

AET - Avionics Electronic Technicians Practice Test

AET - Avionics Electronic Technicians Practice Test

AET Communication Systems 2