The Basic lessons · Interference and suppression · B-008-005

Taming Signals: Filters and Interference Control

Learn how different electronic filters block unwanted radio noise while letting your desired signals pass. Understand why matching impedance prevents signal loss and how to choose the right filter for specific interference problems.

This lesson is part of SignalPrep Pro. The subsection's 11 exam questions are free to practise: practise B-008-005.

What this subsection asks

• What is the frequency response of an ideal notch filter?
• A filter attenuates frequencies below its cut-off frequency of 60 MHz. What type of filter is it?
• What type of filter attenuates RF energy above and below a certain range of frequencies?
• Why should the impedance of a filter match the transmission line where it is inserted?
• Listening to shortwave on a low-cost software defined receiver (SDR), you hear several stations known to operate on much higher frequencies. What type of filter could help?
• You need to install an AC line filter to reduce radio frequency noise heard in your station equipment. What type of frequency response should it have?
• A strong interfering signal is very close to your receive frequency. Which type of filter can effectively suppress it?
• In a Field Day operation with separate transmitters assigned to specific bands, what type of filter is needed on the receivers to minimize interference?
• A nearby high-power HF broadcast station in the 31-metre band is interfering with your reception on the 40-metre and 30-metre bands. What type of filter is needed on the receiver to minimize interference?
• Your 2-metre station suffers receiver overload from several land mobile service transmitters on adjacent bands. What type of filter could help?
• A filter attenuates frequencies above its cut-off frequency of 40 MHz. What type of filter is it?