HAM Radio Extra Class MCQ 4 — Questions and Answers
Question 1: What is the meaning of the Q-signal 'QSB' during an HF contact?
- Your signals are fading (Correct answer)
- Interference from other stations
- Increase your transmitter power
- Change to another frequency
Correct answer: Your signals are fading
QSB means 'your signals are fading' and indicates that signal strength is varying due to propagation changes.
Question 2: In a phase-locked loop (PLL) frequency synthesizer, the voltage-controlled oscillator (VCO) output is divided and compared with:
- The transmitter output power level
- A stable reference frequency from a crystal oscillator (Correct answer)
- The audio input signal
- The antenna SWR
Correct answer: A stable reference frequency from a crystal oscillator
The PLL compares the divided VCO output against a stable crystal reference; the loop filter drives the VCO error toward zero frequency offset.
Question 3: Which propagation mode allows moonbounce (EME) communication?
- Sporadic E
- Earth-Moon-Earth reflection of radio waves (Correct answer)
- F2 skip
- Tropospheric scatter
Correct answer: Earth-Moon-Earth reflection of radio waves
EME uses the Moon as a passive reflector; signals travel ~800,000 km round trip with losses exceeding 250 dB requiring high-gain antennas and sensitive receivers.
Question 4: What is the function of a 'splatter filter' or speech processor in an SSB transmitter?
- To remove hum from the audio
- To limit peak audio levels and improve average power, reducing bandwidth splatter on adjacent channels (Correct answer)
- To separate the two sidebands
- To suppress carrier leakage
Correct answer: To limit peak audio levels and improve average power, reducing bandwidth splatter on adjacent channels
A speech processor increases average modulation power and the splatter filter prevents over-modulation peaks from spreading energy into adjacent channels.
Question 5: Under FCC Part 97, which of the following is a legitimate third-party traffic restriction?
- Third-party traffic is prohibited on all HF bands
- Third-party traffic is banned with countries that have no third-party agreement with the US (Correct answer)
- Third-party messages may only be sent using CW
- Third-party traffic is allowed only on 2 meters and above
Correct answer: Third-party traffic is banned with countries that have no third-party agreement with the US
FCC rules prohibit third-party international traffic with countries that do not have a third-party agreement with the United States.
Question 6: What is the primary advantage of using a helical antenna for satellite communications?
- It requires no ground plane
- It produces circular polarization, reducing polarization mismatch loss with tumbling satellites (Correct answer)
- It has extremely high gain on HF
- It eliminates the need for a preamplifier
Correct answer: It produces circular polarization, reducing polarization mismatch loss with tumbling satellites
Helical antennas radiate circularly polarized waves, which match the polarization of signals from spinning satellites regardless of their orientation.
Question 7: When measuring the noise figure of a receiver, a calibrated noise source is used. What does a lower noise figure indicate?
- More sensitivity loss at high signal levels
- The receiver adds less internal noise and is more sensitive to weak signals (Correct answer)
- Higher power consumption
- Greater selectivity
Correct answer: The receiver adds less internal noise and is more sensitive to weak signals
Noise figure (NF) quantifies how much a receiver degrades signal-to-noise ratio; a lower NF means the receiver introduces less noise and can detect weaker signals.
HAM Radio Extra Class MCQ 4
What is the meaning of the Q-signal 'QSB' during an HF contact?