HAM - Radio Extra Class Test Radio Extra Class General 1 — Questions and Answers
Question 1: What is the lowest frequency on the 40-meter band on which an Amateur Extra class licensee may operate SSB voice?
- 7.000 MHz
- 7.025 MHz
- 7.125 MHz (Correct answer)
- 7.175 MHz
Correct answer: 7.125 MHz
Amateur Extra class licensees hold phone (SSB/voice) privileges beginning at 7.125 MHz on the 40-meter band. General class licensees may only use phone down to 7.175 MHz, so the 7.125–7.175 MHz segment is exclusive to Extra (and Advanced) class operators.
Question 2: Which mode of propagation is responsible for extending 2-meter VHF signals over 1,000 miles or more during periods of stable high-pressure weather systems?
- Sporadic E
- Meteor scatter
- Tropospheric ducting (Correct answer)
- Transequatorial propagation
Correct answer: Tropospheric ducting
Tropospheric ducting occurs when a temperature inversion in the lower atmosphere traps VHF/UHF signals, acting like a waveguide that can carry signals for hundreds to thousands of miles. It is most common during stable, warm, high-pressure conditions.
Question 3: What is the approximate symbol rate of a PSK31 digital mode signal?
- 12.5 baud
- 31.25 baud (Correct answer)
- 300 baud
- 1200 baud
Correct answer: 31.25 baud
PSK31 (Phase Shift Keying, 31 baud) uses a symbol rate of approximately 31.25 baud. This extremely slow rate gives PSK31 a bandwidth of roughly 31 Hz, making it one of the narrowest and most spectrum-efficient HF digital modes.
Question 4: How does the radiation resistance of a folded dipole compare to that of a standard half-wave dipole?
- It is one-quarter as high, approximately 18 ohms
- It is the same, approximately 73 ohms
- It is twice as high, approximately 146 ohms
- It is four times as high, approximately 292 ohms (Correct answer)
Correct answer: It is four times as high, approximately 292 ohms
A folded dipole has a radiation resistance of approximately 292 ohms—four times that of a standard half-wave dipole (~73 ohms). The two parallel conductors share the driven current, and the impedance transformation results in a 4:1 ratio, making the folded dipole a natural match for 300-ohm twin-lead feedline.
Question 5: What is the primary purpose of a key-click filter in a CW transmitter?
- To increase output power during keying
- To lock the oscillator frequency during keying transients
- To smooth the rise and fall times of keyed pulses, reducing occupied bandwidth (Correct answer)
- To sharpen keying edges for maximum code readability
Correct answer: To smooth the rise and fall times of keyed pulses, reducing occupied bandwidth
Abrupt transitions between the on and off states of a CW signal generate broad sidebands known as key clicks that can interfere with adjacent stations. A key-click filter shapes the envelope so that rise and fall times are gradual (typically a few milliseconds), greatly reducing the occupied bandwidth.
Question 6: What two factors primarily determine the Maximum Usable Frequency (MUF) for a specific ionospheric propagation path?
- Transmitter power and antenna height above ground
- The critical frequency of the ionospheric layer and the angle of wave incidence (Correct answer)
- Solar flux index and geomagnetic K-index only
- Time of day and geographic distance between stations
Correct answer: The critical frequency of the ionospheric layer and the angle of wave incidence
The MUF equals the critical frequency of the relevant ionospheric layer divided by the cosine of the angle of incidence (the secant law: MUF = Fc × sec θ). A lower radiation angle increases the secant factor, raising the MUF. Both the layer's critical frequency and the wave's angle of incidence must be known to calculate it.
HAM - Radio Extra Class Test Radio Extra Class General 1
What is the lowest frequency on the 40-meter band on which an Amateur Extra class licensee may operate SSB voice?