Re: 25 ohm coax cable

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Article #10965

#10965

From: Richard A. Schumacher
Date: Thu, 08 Oct 1992 17:48

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Putting two 50 ohm cables in parallel yields 25 ohms. The 
parallel capacitances add, and the parallel inductances
are, well, parallel; so the per-unit-length capacitance 
seen by the driver is doubled and the per-unit-length 
inductance seen by the driver is halved. This halves the 
impedance. (Doubters are invited to whip out their HP
54120 or equivalent time-domain reflectometer and check it
out for themselves.) However, this may be an awkward solution
because it requires carefully time matching the lengths of
the parallel 50 ohm coaxes.

What is your circuit? Why does it specify 25 ohms? Another
solution may be possible.

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Message-ID: <schumach.718566536@convex.convex.com>

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References: <1992Oct5.142505.23001@dxcern.cern.ch> <bvr5pd.14o@wang.com> <1992Oct8.120225.6247@fys.ruu.nl>

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Path: arc1-ca.pugleaf.net!sparky!uunet!pmafire!news.dell.com!swrinde!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!convex!schumach
From: schumach@convex.com (Richard A. Schumacher)
Subject: Re: 25 ohm coax cable
Message-ID: <schumach.718566536@convex.convex.com>
Keywords: coax cable
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Organization: CONVEX Computer Corporation, Richardson, Tx., USA
References: <1992Oct5.142505.23001@dxcern.cern.ch> <bvr5pd.14o@wang.com> <1992Oct8.120225.6247@fys.ruu.nl>
Date: Thu, 8 Oct 1992 17:48:56 GMT
X-Disclaimer: This message was written by a user at CONVEX Computer
              Corp. The opinions expressed are those of the user and
              not necessarily those of CONVEX.
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