Basic Qualification · B-003 Station assembly, practice and safety · B-003-010-011
When receiving CW, which of these frequency ranges is optimum for a band-pass filter?
- A 300 Hz to 2700 Hz
- B 100 Hz to 1100 Hz
- C 750 Hz to 850 Hz
- D 2100 Hz to 2300 Hz
Correct answer: C — 750 Hz to 850 Hz. From the official ISED question bank, verified word for word.
Why
CW signals are Morse code tones, and the human ear hears them best when the tone is around 750 to 850 hertz. The full explanation — and one for every question — is in Pro.
Practise this section
Building a station safely: power supplies, grounding, RF exposure, lightning, feedline routing, and what a transmitter, receiver and transceiver actually do.