HAM Radio Extra Class MCQ 5 — Questions and Answers
Question 1: What is the maximum symbol rate permitted for RTTY or data emissions in the 80-meter amateur band below 3600 kHz?
- 300 baud (Correct answer)
- 1200 baud
- 56 kilobaud
- 19.6 kilobaud
Correct answer: 300 baud
FCC Part 97.307 limits the symbol rate to 300 baud for RTTY and data emissions below 28 MHz (including 80 meters).
Question 2: A buffer amplifier is placed between a VFO and subsequent amplifier stages primarily to:
- Boost output power to legal limit
- Isolate the oscillator from load variations that could cause frequency pulling (Correct answer)
- Convert AM to FM
- Filter harmonic content from the carrier
Correct answer: Isolate the oscillator from load variations that could cause frequency pulling
Buffer amplifiers present a constant, high-impedance load to the oscillator, preventing output loading from shifting the oscillation frequency.
Question 3: What phenomenon causes a received signal to vary rapidly in strength and phase when the receiving antenna is moved only a fraction of a wavelength?
- Tropospheric ducting
- Multipath fading due to constructive and destructive interference of reflected waves (Correct answer)
- Ionospheric absorption
- Receiver desensitization
Correct answer: Multipath fading due to constructive and destructive interference of reflected waves
Multipath fading occurs when multiple reflected signal paths arrive with different delays, causing phase differences that alternately add or cancel.
Question 4: Which parameter best describes the ability of a receiver to reject an interfering signal on an adjacent channel?
- Noise figure
- Selectivity (Correct answer)
- Sensitivity
- Dynamic range
Correct answer: Selectivity
Selectivity describes how well a receiver attenuates signals outside its passband, determining adjacent-channel rejection.
Question 5: What is a 'Doherty amplifier' and why is it used in modern RF transmitters?
- A push-pull amplifier for audio frequency stages
- An efficiency-enhancing amplifier topology that keeps efficiency high across a wide range of output power levels (Correct answer)
- A balanced amplifier using two identical modules for redundancy
- An amplifier with automatic gain control for stable output
Correct answer: An efficiency-enhancing amplifier topology that keeps efficiency high across a wide range of output power levels
The Doherty architecture uses a carrier and peaking amplifier to maintain high efficiency (close to Class B) even at power back-off levels typical of modulated signals.
Question 6: Under FCC Part 97, what must a licensee do before operating a station in a foreign country?
- File a FCC Form 605 at least 30 days in advance
- Obtain permission from the foreign country's telecommunication authority and comply with the terms of any applicable reciprocal agreement (Correct answer)
- Obtain a Technician upgrade to permit international operation
- No action needed; US Amateur licenses are globally valid
Correct answer: Obtain permission from the foreign country's telecommunication authority and comply with the terms of any applicable reciprocal agreement
Operation in a foreign country requires compliance with that country's regulations and any bilateral or CEPT/IARU reciprocal operating agreement.
Question 7: What is the advantage of a superheterodyne receiver over a tuned radio frequency (TRF) receiver?
- Simpler circuit with fewer stages
- Consistent selectivity and gain because amplification is done at a fixed intermediate frequency (Correct answer)
- Lower power consumption at all frequencies
- Elimination of the need for an RF amplifier stage
Correct answer: Consistent selectivity and gain because amplification is done at a fixed intermediate frequency
By converting the incoming signal to a fixed IF, a superhet achieves stable, optimized filtering and gain that would be impossible to maintain across a wide tuning range.
HAM Radio Extra Class MCQ 5
What is the maximum symbol rate permitted for RTTY or data emissions in the 80-meter amateur band below 3600 kHz?