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Path: utzoo!watmath!clyde!caip!andromeda!argus!ron
From: ron@argus.UUCP (Ron DeBlock)
Newsgroups: net.audio,net.analog
Subject: Re: need interconnect cable recommendations...
Message-ID: <328@argus.UUCP>
Date: Sat, 12-Jul-86 10:22:44 EDT
Article-I.D.: argus.328
Posted: Sat Jul 12 10:22:44 1986
Date-Received: Sun, 13-Jul-86 04:30:33 EDT
References: <2107@orca.UUCP> <926@ihu1g.UUCP> <1225@uwmcsd1.UUCP>
Distribution: na
Organization: NJ Inst of Tech., Newark NJ
Lines: 42
Xref: watmath net.audio:8946 net.analog:941
Summary: a few questions...

In article <1225@uwmcsd1.UUCP>, shop@uwmcsd1.UUCP (Thomas Krueger) writes:
> > Much of this stuff has aluminum shielding and a copper-plated iron core 
> > (read: CHEAP!).  Some of the better stuff has copper shielding and a copper
> > core, but I think that Radio Hack carries the cheapo stuff.  Not only is
> > it a bitch to work with, even in video applications, but the aluminum-shielded
> > stuff is impossible to solder (read: BAD CONNECTION).  Finally, all RG-59
> > has a solid core, which, if you're concerned about skin effect, is decidedly
> > not the thing to use as an interconnect.
> 
> Belden makes an RG-59/U with copper 22 guage (7X30) center conductor and
> 95% coverage copper shielding for CCTV applications... the number is
> 9259, the attenuation (from the book) is 2.1 dB per foot at 50 MHz.
                                           ^^^^^^^^^^^^^^^^^^^^^^^^^
> Nominal impedance is 75 ohms.
> 

Hmmm, I usually see specs for dB attenuation per 100 feet.  2.1 dB/foot
at 50 MHz is VERY bad.  A mistake, maybe? :-)

I have a couple of questions I would like to know the answer to:

1) Just how important is the skin effect at audio frequencies?  Audio is
pretty low on the spectrum, I wouldn't think it would be that big of
a problem.

2) What about impedence mismatch?  With a 75 ohm transmission line connected
to a 4 or 8 ohm load, I would expect quite a bit of reflected power.  Or
doesn't that matter at audio frequencies?

Please try to back up your answers with calculations or actual measurements,
there's enough guessing/speculation/quoting of manufacturer's (somewhat
dubious) specs on the net.

-- 
Ron DeBlock	KA2IKT

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