Stan, you asked a good question-- one I asked about some time ago. When I worked in the aerospace industry, I designed and used analog and digital filters for measurement applications. Most textbook design formulas and procedures are based on 3 dB bandwidths, although sometimes our measurement requirements demanded 0.5 dB bandwidth.
Amateur radio IF bandwidths seem to have been standardized at the 6dB points. If the filter designers are reporting 3 dB points, this might account for the difference you asked about. BTW, I just checked the INRAD website and looked for the filter curves for the K3 roofing filters and couldn't find them. They used to be available there. 73, Chuck NI0C K2-10 s/n 5853 K3 s/n 1061 Stan Rife, W5EWA, wrote: "I'm not sure why a filter would be advertised as a 250hz filter but actually have a (usable?) bandwidth of 370hz. Is this just a difference in how it's measured? " ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
