Wayne, I realize that I'm showing my ignorance, but could you briefly explain how a "dual-passband filter" works in the K3?? I would DEFINITELY be interested in either of the two possibilities you mentioned for my RTTY usage, even though the 8 pole 400 cycle one is pretty good. 73, Don, WB5HAK ----- Original Message ----- From: "Wayne Burdick" <n...@elecraft.com> To: "Jim Brown" <j...@audiosystemsgroup.com> Cc: <elecraft@mailman.qth.net> Sent: Thursday, July 15, 2010 1:01 PM Subject: Re: [Elecraft] Let's Try This Again -- was "[K3] ... A 750 Hz,8-Pole ... Filter?"
> It *is* difficult to build very narrow 8-pole filters with low loss. > That's one reason Elecraft offers a 5-pole, 200-Hz unit. > > 5 poles is entirely adequate at these narrow widths. Our 2-kHz IMD > dynamic range using the 200-Hz filter is outstanding. > > We've had some requests to offer a 270 or 300-Hz 5-pole filter, which > would be better optimized for narrow-shift RTTY than the 200-Hz > filter. We're also considering a dual-passband filter (500/270 or > 500/300) that would fit in one slot. > > 73, > Wayne > N6KR > > > On Jul 15, 2010, at 10:18 AM, Jim Brown wrote: > >> On Thu, 15 Jul 2010 14:53:10 +0100, Ian White GM3SEK wrote: >> >>> Agreed. 250-270Hz would be the "sweet spot" for an 8-pole filter, to >>> guarantee good sales for the manufacturer *and* good performance >>> for a >>> range of users in heavy QRM. >> >>> Now let's see if Inrad or Elecraft take the bait :-) >> >> Hang on a minute, guys. Inrad builds a nominal 250 Hz filter, Elecraft >> tests and re-sells it, and we buy it, because we've agreed that it's a >> sweet spot operationally. >> >> The issue is that it's wider than than at the -3dB points. So the >> problem appears to be that it's pretty difficult to build an 8-pole >> 250 >> Hz filter at 8.8 MHz, and that Inrad has given up on doing better. >> >> 73, Jim K9YC >> >> >> ______________________________________________________________ >> 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 > > ______________________________________________________________ > 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 > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.839 / Virus Database: 271.1.1/3007 - Release Date: 07/15/10 06:09:00 ______________________________________________________________ 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
