Basic Qualification · B-008 Interference and suppression · B-008-004-001
If a neighbour reports television interference on one or two channels only when you transmit on 15 metres, what is probably the cause of the interference?
- ASplatter due to overmodulation
- BTelevision receiver front-end overload
- CParasitic oscillations from your transmitter
- DHarmonic emissions from your transmitter
Correct answer: D — Harmonic emissions from your transmitter. From the official ISED question bank, verified word for word.
Why
Harmonic emissions are unwanted signals your transmitter creates at multiples of your operating frequency; on 15 metres, the second harmonic lands right in the VHF television band, causing interference on specific channels. The full explanation — and one for every question — is in Pro.
Practise this section
Interference and suppression is section B-008 of the Basic exam: When things interfere: harmonics, overload, RFI to and from your station, filters, ferrites and how to fix the neighbour's TV.
Drill B-008 — free, no account