Pardon me, but an elliptic filter does not tend toward infinite attenuation in the stopband! The tradeoff, with elliptical filter designs, in which we incorporate transmission zeroes to increase the cutoff rate into the stopband, is finite attenuation in the stopband. Indeed, ultimate attenuation and ripple are essential specifications that must be incorporated into the design of an elliptical filter. If really high values of attenuation are required the elliptic filter can be followed by Butterworth or other all-pole filter section(s)
73, Charlie, K4OTV -----Original Message----- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Chuck Hutton Sent: Monday, September 22, 2014 3:22 PM To: topband@contesting.com Subject: Re: Topband: BCB interference ? Their description (to me at least) indicates an elliptic filter with a stopband peak of -40 dB at 1 MHZ and ranging to infinity (in theory) elsewhere in the stopband. In other words, 40 dB is the maximum for the discrimination factor. "Indicates" is a word I feel is necessary as their filter really is poorly described. They should have said what filter type and order are used and used standard nomenclature for filter parameters. And there's no mention of passband ripple. Chuck > Date: Mon, 22 Sep 2014 11:21:29 -0700 > From: j...@audiosystemsgroup.com > To: topband@contesting.com > Subject: Re: Topband: BCB interference ? > > On Mon,9/22/2014 6:50 AM, Ed Stallman wrote: > > Has anyone used this High Pass Filter ? > > http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html > > The spec for this filter is ambiguous. Is the -40dB at all frequencies > below 1.6 MHz, or at 1 MHz? BIG difference. OTOH, the Dunestar > filters are decent for the price. > 73, Jim K9YC _________________ Topband Reflector Archives - http://www.contesting.com/_topband --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _________________ Topband Reflector Archives - http://www.contesting.com/_topband