HAM Practice Questions 4 — Questions and Answers
Question 1: What is the significance of the 'quiet zone' surrounding the National Radio Astronomy Observatory in Green Bank, West Virginia?
- Amateur operation is prohibited within 100 miles
- Strict power and emission controls apply to protect sensitive radio telescope receivers (Correct answer)
- Only CW operation is permitted in the area
- The zone requires special FCC experimental licenses
Correct answer: Strict power and emission controls apply to protect sensitive radio telescope receivers
The National Radio Quiet Zone around Green Bank imposes power limits and emission restrictions to protect the extremely sensitive radio telescope receivers from interference.
Question 2: Which type of filter has a maximally flat response in the passband but a relatively slow roll-off outside it?
- Chebyshev filter
- Butterworth filter (Correct answer)
- Elliptic filter
- Bessel filter
Correct answer: Butterworth filter
A Butterworth filter is designed for a maximally flat magnitude response in the passband, sacrificing roll-off steepness compared to Chebyshev or elliptic designs.
Question 3: What is 'reciprocal mixing' in a receiver and what causes it?
- Mixing of two desired signals producing a sum frequency
- Phase noise on the local oscillator mixing with a strong off-channel signal to produce interference in the IF (Correct answer)
- Cross-modulation from an overloaded RF amplifier stage
- Image rejection failure in a double-conversion design
Correct answer: Phase noise on the local oscillator mixing with a strong off-channel signal to produce interference in the IF
Reciprocal mixing occurs when the local oscillator's phase noise sidebands mix with a strong nearby signal, creating noise that falls in the IF passband and raises the receiver noise floor.
Question 4: What emission type is used when an Extra class operator transmits RTTY on HF?
- F1B
- J2B (Correct answer)
- A1A
- G1B
Correct answer: J2B
RTTY using SSB audio tones (AFSK) is designated J2B — J for single-sideband suppressed carrier, 2 for a digital sub-carrier, and B for telegraphy.
Question 5: What is the purpose of a 'loading coil' placed at the base of a short vertical antenna?
- To increase the antenna's radiation resistance
- To resonate the electrically short antenna at the operating frequency by adding inductive reactance (Correct answer)
- To provide a DC ground path for lightning protection
- To match the antenna impedance to exactly 50 ohms
Correct answer: To resonate the electrically short antenna at the operating frequency by adding inductive reactance
A loading coil adds inductive reactance to cancel the capacitive reactance of an electrically short antenna, bringing it into resonance at the desired frequency.
Question 6: According to FCC rules, under what condition may an amateur station transmit music?
- Never under any circumstance
- Only when incidental to an authorized retransmission of space shuttle communications (Correct answer)
- When the music is copyright-free
- During special event stations with a one-day license
Correct answer: Only when incidental to an authorized retransmission of space shuttle communications
FCC Part 97.113 prohibits music transmission except when it is incidental to an authorized retransmission of NASA manned spacecraft communications.
Question 7: What is the velocity factor of a transmission line and how does it affect electrical length?
- It is the ratio of signal velocity in the line to the speed of light; a lower factor makes the line electrically longer (Correct answer)
- It is the ratio of line impedance to free-space impedance; higher values reduce SWR
- It is the power loss per unit length; lower values indicate better cable quality
- It is the phase shift per meter; higher values indicate more dispersion
Correct answer: It is the ratio of signal velocity in the line to the speed of light; a lower factor makes the line electrically longer
Velocity factor (VF) is the ratio of signal propagation speed in the line to the speed of light in a vacuum; a VF less than 1 means a physical length is electrically longer than the same length in free space.
HAM Practice Questions 4
What is the significance of the 'quiet zone' surrounding the National Radio Astronomy Observatory in Green Bank, West Virginia?