The Basic lessons · Interference and suppression · B-008-004

Harmonics, Splatter, and Out-of-Band Emissions

Learn why transmitters sometimes send signals on the wrong frequencies and how to stop them. Understand the difference between harmonics, splatter, and out-of-band emissions to keep your neighbours happy.

This lesson is part of SignalPrep Pro. The subsection's 11 exam questions are free to practise: practise B-008-004.

What this subsection asks

• 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?
• What are harmonic emissions?
• Why are harmonic emissions from an amateur radio station not wanted?
• What term describes unwanted radio energy transmitted just outside the necessary bandwidth?
• If you are told your station was heard on 21.375 MHz but at the time you were operating on 7.125 MHz. What is one reason that could cause this to happen?
• What causes splatter interference?
• A television tuned to channel 3 (60 MHz - 66 MHz) experiences interference when you are transmitting on the 15-metre band. Other channels are not affected. What is the most likely cause?
• What is the probable cause of "flat topping" (non-linear operation) of an amplifier in an SSB transmitter?
• Which of the following may cause excessive harmonics in a transmitter?
• An interfering signal from an HF transmitter is found to have a frequency of 56 MHz. What could be the source?
• Harmonics may be produced in the RF power amplifier of a transmitter if: