Basic Qualification · B-003 Station assembly, practice and safety · B-003-019-008
You are using an HF off-centre-fed (OCF) unbalanced antenna. When you transmit on SSB, distorted audio and noise are heard from an outboard amplified speaker. What device could you install in the transmission line to mitigate this problem?
- AA low-pass filter
- BA surge suppressor
- CAn antenna tuner
- DA common-mode choke
Correct answer: D — A common-mode choke. From the official ISED question bank, verified word for word.
Why
A common-mode choke stops unwanted radio frequency current from flowing along the outside of your coaxial cable, which is what causes the distorted audio and noise in your speaker. The full explanation — and one for every question — is in Pro.
Practise this section
Station assembly, practice and safety is section B-003 of the Basic exam: Building a station safely: power supplies, grounding, RF exposure, lightning, feedline routing, and what a transmitter, receiver and transceiver actually do.
Drill B-003 — free, no account