Practice
Radio Theory — Practice
How signals are generated, modulated, transmitted and recovered. Untimed topic practice with a full explanation after every question, so a wrong answer becomes a study note rather than a dead end.
Questions
12
Time limit
Untimed
Pass mark
60%
Before you start
- Untimed. The explanation appears as soon as you answer, because the point here is to learn rather than to score.
- Mark an answer as a guess and it enters your review queue even if it happened to be right.
- Every answer moves your ability estimate for that topic and updates your readiness score.
- Retake as often as you like.
Sample questions
What is the approximate wavelength of a signal at 150 MHz?
- 0.5 m
- 2 m
- 20 m
- 50 m
Why 2 m is right: Wavelength in metres ≈ 300 ÷ frequency in MHz = 300 ÷ 150 = 2 metres. That is why the 144 MHz band is called the '2 metre' band.
At what speed do radio waves travel in free space?
- 300 metres per second
- 300 kilometres per second
- 300,000 kilometres per second
- It depends on the frequency
Why 300,000 kilometres per second is right: Radio waves travel at the speed of light, approximately 300,000 km per second (3 × 10⁸ m/s), regardless of frequency.
The second harmonic of a 7.05 MHz transmission appears at:
- 3.525 MHz
- 7.05 MHz
- 14.1 MHz
- 21.15 MHz
Why 14.1 MHz is right: Harmonics are integer multiples of the fundamental. The second harmonic is 2 × 7.05 = 14.1 MHz. Harmonic radiation is a common cause of out-of-band interference.