Basic Qualification · B-003 Station assembly, practice and safety · B-003-010-010
A communications receiver has four filters installed in it, respectively designated as 250 Hz, 500 Hz, 2.4 kHz and 6 kHz. You are copying a CW transmission and there is a great deal of interference. Which one of the filters would you choose?
- A 6 kHz
- B 250 Hz
- C 500 Hz
- D 2.4 kHz
Correct answer: B — 250 Hz. From the official ISED question bank, verified word for word.
Why
CW signals, which are Morse code tones, are very narrow in frequency, so a 250 Hz filter blocks the widest range of unwanted noise and interference while letting the signal through. 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.