What Are Roofing Filters?

Amateur Radio

• Roofing filters are used by individuals who operate amateur radios, commonly referred to as "ham" radios. In the United States, these radios are regulated by the Federal Communications Commission. Would-be operators must first receive a license from the FCC before they can operate an amateur radio set.

Roofing Filters

• A roofing filter is used by a ham radio operator to limit the radio's first intermediate frequency. A ham radio takes radio signals, known as radio frequency, or RF, and converts them into audio information. The radio receiver converts the RF into an intermediate frequency, or IF, before it transforms it into audio information. The roofing filter limits the range of frequencies that are transformed into this intermediate frequency.

Roofing Filter Function

• Roofing filters act as a shield, protecting an amateur radio from unwanted frequencies. The filter protects the radio by ensuring that only a limited range of frequencies progress to other radio systems, such as the amplifiers and mixers. The term "roofing filter" is somewhat of a misnomer, as these filters shield the radio system from both unwanted higher and lower frequency signals. To use a metaphor, if your home is your radio, a roofing filter is both the roof that keeps rain from getting in by coming from the top and the water-proof basement that prevents water getting in by coming through the bottom.

Licensing

• Since the passing of the Radio Act 1912, the U.S. government has regulated amateur radio operations in some way. All amateur radio operators must obtain their operator's license from the FCC by first completing an amateur radio license examination. There are three license classes available: Amateur Extra Class, General Class and Technician Class.