HAM Radio Extra Class MCQ 3 — Questions and Answers
Question 1: What is the purpose of a Smith chart in antenna and transmission line work?
- To plot signal strength vs. frequency
- To graphically represent impedance and facilitate matching network design (Correct answer)
- To calculate ionospheric skip distance
- To measure modulation percentage
Correct answer: To graphically represent impedance and facilitate matching network design
A Smith chart is a graphical tool for visualizing complex impedances and designing impedance matching networks for antennas and transmission lines.
Question 2: What condition causes an amplifier to produce intermodulation distortion products at frequencies 2f1−f2 and 2f2−f1?
- Linear operation with high gain
- Third-order nonlinearity in the active device (Correct answer)
- Excessive forward bias
- Impedance mismatch at the input
Correct answer: Third-order nonlinearity in the active device
Third-order nonlinearity generates intermodulation products that fall close to the original frequencies, making them difficult to filter.
Question 3: What is the radiation resistance of a typical half-wave dipole in free space?
- 50 ohms
- 73 ohms (Correct answer)
- 300 ohms
- 150 ohms
Correct answer: 73 ohms
A half-wave dipole in free space has a radiation resistance of approximately 73 ohms.
Question 4: Automatic Link Establishment (ALE) is primarily used in which amateur radio context?
- Automatically tuning an antenna
- Establishing HF digital voice and data links by scanning frequencies for best propagation (Correct answer)
- Controlling repeater access
- Synchronizing clock signals for digital modes
Correct answer: Establishing HF digital voice and data links by scanning frequencies for best propagation
ALE systems automatically scan frequencies and handshake to select the best-propagating channel before establishing an HF link.
Question 5: In amateur radio, what is meant by 'gray line' propagation?
- Static on the 80-meter band
- Enhanced propagation along the terminator between day and night on Earth (Correct answer)
- Multipath fading on VHF
- Ducting caused by temperature inversions
Correct answer: Enhanced propagation along the terminator between day and night on Earth
The gray line is the twilight zone between daylight and darkness where the absorbing D layer is absent, allowing strong long-distance propagation.
Question 6: What is the primary function of a transverter?
- Converts AC mains to DC supply voltage
- Translates signals from one frequency band to another for use with a base-rig (Correct answer)
- Matches impedance between antenna and coax
- Converts FM audio to SSB
Correct answer: Translates signals from one frequency band to another for use with a base-rig
A transverter mixes a lower-frequency rig's output to a higher band (e.g., HF rig → microwave), enabling operation on bands the rig does not cover.
Question 7: Which filter type provides the sharpest roll-off at the cutoff frequency but exhibits the most ringing with pulsed signals?
- Butterworth
- Bessel
- Chebyshev
- Elliptic (Cauer) (Correct answer)
Correct answer: Elliptic (Cauer)
Elliptic (Cauer) filters have the steepest roll-off for a given order but produce significant transient ringing due to equiripple in both pass and stop bands.
HAM Radio Extra Class MCQ 3
What is the purpose of a Smith chart in antenna and transmission line work?