Date: Wed, 23 Feb 94 04:30:07 PST
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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
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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).
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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.
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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
-------------------------------------------------------------------------
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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
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End of Info-Hams Digest V94 #194
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