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- Date: Wed, 23 Feb 94 04:30:07 PST
- From: Info-Hams Mailing List and Newsgroup <info-hams@ucsd.edu>
- 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: <Info-Hams@UCSD.Edu>
- Send subscription requests to: <Info-Hams-REQUEST@UCSD.Edu>
- 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
- ******************************
-