On a recent club net, one of the stations checking in, asked about roofing filters. The roofing filter in a radio is the filter through which the first IF must pass. According to Elecraft, the term "roofing filter" has most often been used in relation to triple- or quadruple-conversion receivers. Such receivers have an IF above the highest RF band covered; it's typically something in the range of 30 to 70 MHz or higher. But "roofing" as a term should be interpreted as "protective," not "high in frequency." A roofing filter protects later stages, including amplifiers, mixers, narrower filters, and DSP subsystems, just as the roof on your house keeps rain out of all of the rooms.
Jeff K3JRZ stopped at US-10688 Tubmill Pond State Fishing Lake @delawarednrec, in Milford, Delaware, on Friday March 29, 2024, for his first Parks On The Air @ParksOnTheAir (POTA) activation after the ISO-3166 standard change to U.S. POTA entities. Previously, all U.S. parks were defined by the prefix KILO "K."