Basic Qualification · B-008 Interference and suppression · B-008-004-008
What is the probable cause of "flat topping" (non-linear operation) of an amplifier in an SSB transmitter?
- A Defective sideband filter
- B Insufficient power supply current capacity
- C Defective low-pass filter
- D Excessive microphone gain
Correct answer: D — Excessive microphone gain. From the official ISED question bank, verified word for word.
Why
Excessive microphone gain drives the amplifier beyond its limits, forcing it to clip the peaks of the audio signal and creating a distorted, flattened waveform known as flat topping. The full explanation — and one for every question — is in Pro.
Practise this section
When things interfere: harmonics, overload, RFI to and from your station, filters, ferrites and how to fix the neighbour's TV.