Never mind, it was answered. Carl
----- Original Message ----- From: "ZR" <[email protected]> To: "Paul Christensen" <[email protected]>; <[email protected]> Sent: Friday, July 13, 2012 8:44 PM Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > > ----- Original Message ----- > From: "Paul Christensen" <[email protected]> > To: <[email protected]> > Sent: Friday, July 13, 2012 5:04 PM > Subject: Re: Topband: Mother of all ferrite common-mode coaxial chokes > > >>> One of the dumbest things I've seen recently from a very good company is >>> RF chokes in series with the shield connections on analog and RS232 I/O >>> boards for the Elecraft K3. >> >> Right. I think Joe, W4TV, was one of the first to identify that problem >> back around 2008. Many of us quickly jumpered the handful of RFCs used >> on >> shield leads of the RS232 I/O Board. Until revised by the factory, that >> board was the Achilles Heel of the K3. >> >>> Modern pro output stages have a very low source Z (typically >>> 100 ohms for line level) and high input Z (typically 10K for line >>> level), and consumer stuff is roughly 3-5X those values. >> >> Somewhere in my files from the late '80s is a white paper authored by >> Richard Cabot. I believe Richard was the chief designer of the Audio >> Precision brand of audio test equipment. The focus of the article was on >> the standarding of all audio output stages, balanced or unbalanced to a >> value of 40-50 ohms. He created models showing the effect of changing >> drive >> Z from 1-ohm through 600-ohms into long audio cables (and independent of >> terminating Z) that start to take on transmission line qualities. His >> conclusion was that a target of just under 50 ohms was optimum. >> >> Paul, W9AC >> > > What does he consider a long audio cable Paul? Ive been using 600 Ohms to > run studio type equipment for the AM station. > > Carl > KM1H > > >> _______________________________________________ >> UR RST IS ... ... ..9 QSB QSB - hw? BK >> >> >> ----- >> No virus found in this message. >> Checked by AVG - www.avg.com >> Version: 10.0.1424 / Virus Database: 2437/5129 - Release Date: 07/13/12 >> > > _______________________________________________ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2437/5130 - Release Date: 07/13/12 > _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
