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[TowerTalk] coax attentuation

To: <>
Subject: [TowerTalk] coax attentuation
From: (Al Williams)
Date: Tue, 8 Jan 2002 01:50:22 -0800

----- Original Message -----
From: "Al Williams" <>
To: <>
Sent: Monday, January 07, 2002 11:21 PM
Subject: coax loss

 I have been trying to determine signal loss in coax by using a dual trace
oscilloscope (Tek 465) connected to the input and output of the coax.
However, instead of a loss I
 am observing a gain!

   My setup is using a MFJ-249 SWR Analyzer as the source and a BNC 51 ohm
 resistor connected to the source.  The opposite end of the coax is
 to the scope and a 51 ohm carbon resistor with short leads.  Both resistors
 measure low swr (<l.2) with the MFJ.

 The waveforms on input and output of the coax appear undistorted sinewaves
 but the output is greater than the input for frequencies up to about 30
mhz. The output
 increases as the coax length increases being about 20% greater with 130' of
LM400.  The MFJ
 measures SWR of about 2:1 (note; the two 50 ohm resistors at input and
output are in

 Has anyone used this method?  What might be wrong with my setup?


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