Date: Wed, 23 Feb 94 04:30:07 PST From: Info-Hams Mailing List and Newsgroup Errors-To: Info-Hams-Errors@UCSD.Edu Reply-To: Info-Hams@UCSD.Edu Precedence: Bulk Subject: Info-Hams Digest V94 #194 To: Info-Hams Info-Hams Digest Wed, 23 Feb 94 Volume 94 : Issue 194 Today's Topics: Coax minimum-loss impeance Dayton parking DIY Audio Notch Filter ? Public Apology Send Replies or notes for publication to: Send subscription requests to: Problems you can't solve otherwise to brian@ucsd.edu. Archives of past issues of the Info-Hams Digest are available (by FTP only) from UCSD.Edu in directory "mailarchives/info-hams". We trust that readers are intelligent enough to realize that all text herein consists of personal comments and does not represent the official policies or positions of any party. Your mileage may vary. So there. ---------------------------------------------------------------------- Date: Tue, 22 Feb 1994 20:12:03 GMT From: elroy.jpl.nasa.gov!sdd.hp.com!hp-cv!hp-pcd!hpcvsnz!tomb@ames.arpa Subject: Coax minimum-loss impeance To: info-hams@ucsd.edu I recently wrote: : OK, carrying this one step further, the outer-diameter/inner-diameter : ratio for min loss under these conditions is 3.59:1. With air : dielectric, this is the 77 ohm cable. But if the dielectric is : polyethelene, commonly used in WWII vintage cables, the impedance : is ... 51.02 ohms! By the way, doing the same thing for solid : Teflon gives 52.9 ohms, still really close to 50. Some follow-up thoughts to this. Independent of impedance, and indpendent of conductor configuration (coaxial, 2-wire open line, 4-wire line, twin-ax, etc.), if you start with air-insulated line and replace the air with dielectric with a dielectric contstant greater than air, the impedance of the line will drop. Under matched condtions (which will be the lowest loss for that line), you would have to put more current in the line for the same power delivered to the load. Because the increased current causes greater I^2*R loss in the conductors, the line will have greater loss than the air-insulated line--even with a dielectric which is completely non-dissipative. If you then make the conductor(s) smaller to get back to the original impedance in the same volume, you will further increase the line loss. If you can use the same condutors at a higher impedance, the loss will be lower: you can do this with open-wire line, at least up to the point where the spacing allows radiation that significantly adds to the loss (and might also cause other problems, like messing up an antenna pattern or causing a security leak). ------------------------------ Date: 22 Feb 1994 20:36:40 GMT From: elroy.jpl.nasa.gov!swrinde!cs.utexas.edu!geraldo.cc.utexas.edu!astro.as.utexas.edu!oo7@ames.arpa Subject: Dayton parking To: info-hams@ucsd.edu pat.wilson@pplace.com (Pat Wilson) reports: >>I have heard many, many, many from this area who are not interested if >>they have to walk everywhere. Seems the buses would make them a small >>fortune if they were circumspect. Oh well. This sort of conjures up the stereotype of the ham who is too lazy to get out of his operating chair and walk somewhere. Someone once told me that Real DXers[tm] have country counts equal to their weight in lbs. ------------------------------ Date: 22 Feb 1994 20:22:16 GMT From: elroy.jpl.nasa.gov!swrinde!gatech!europa.eng.gtefsd.com!library.ucla.edu!news.mic.ucla.edu!unixg.ubc.ca!otter.mech.ubc.ca!harland@ames.arpa Subject: DIY Audio Notch Filter ? To: info-hams@ucsd.edu Does anybody have plans for a DIY audio notch filter ? Am I looking to build one that has both variable centre frequency and bandwidth. MFJ sell a unit that is just what I am looking for, but the price is more than I am will to pay. In their unit you can adjust both centre frequency and bandwidth independently. I have found a circuit that uses an OP-amp and three resistors. The problem is that it is not possible to vary the bandwith / centre frequency with out messing up the other or the gain. I suppose this circuit may work but it would not be very useable. I am not a elecronics wiz but I have built circuits in the past, so I am not afraid to give this a try. Thanks, Harland -- ------------------------------------------------------------------------- Harland MacKenzie "Once you have eliminated Department of Mechanical Engineering the impossible, what ever University of Brithish Columbia remains, no matter how Vancouver, B.C. Canada improbable, must be the truth", Internet: harland@mech.ubc.ca Sir Arthur Conan Doyle CompuServe: 72162,2245 ------------------------------------------------------------------------- ------------------------------ Date: Tue, 22 Feb 1994 20:07:48 GMT From: elroy.jpl.nasa.gov!usc!howland.reston.ans.net!gatech!udel!news.sprintlink.net!direct!kg7bk@ames.arpa Subject: Public Apology To: info-hams@ucsd.edu >In article <2k49diINNmp0@abyss.West.Sun.COM> myers@pongo.West.Sun.COM >-(Dana Myers ) writes: >You're missing the point entirely! Either that or you refuse to see it. >The "Jeff Gold" post was intentionally insulting and inflammatory, and I want to publicly appologize to any innocent party I have offended with my humor. Anyone who knows me will tell you I am a gentleman devil's advocate with an offbeat sense of humor. The "Jeff Gold" post was 100% black humor... I meant to poke fun at Jeff, not insult him... you know, let he who is without sin cast the first stone...the pot calling the kettle black... sacarsm... I've also apologized to Jeff in private. >it completely flies in the face of your earlier statement that Jeff >Gold is "less than human". Please forgive my bad spelling. The statement should have been, "Anyone who calls another a liar in public is less than humane." I still believe that... most people over 45 do believe that way. >Attacking Jeff Gold because you don't >like his postings *doesn't* belong on rec.radio.amateur.misc It wasn't an attack. It was my feebleminded attempt at humor. But you believe it is OK to call an individual a liar on rec.radio.amateur. misc???? This all started when Jeff posted his two-year old, archived flame against Ramsey. I didn't object to his or anybody else's slam of Ramsey products. I objected to his emotional outburst and airing his private dirty laundry agenda (for the Nth time) on a technical news group. I poked fun at Jeff... nothing more. >Does anyone else see the irony?... Jeff NH6IL Yup, someone bad-mouthing a bad-mouther for bad-mouthing a bad-mouther seems ironic to me and most of my Internet friends are still laughing. Again, I'm truly sorry if I offended any innocent party. 73, Cecil, KG7BK ------------------------------ Date: (null) From: (null) Derek "cab!" Wills (AA5BT, G3NMX) Department of Astronomy, University of Texas, Austin TX 78712. (512-471-1392) oo7@astro.as.utexas.edu ------------------------------ End of Info-Hams Digest V94 #194 ******************************