[BC] Xmitters at aol.com

[K7qa@aol.com]

In a message dated 4/10/2007 9:20:31 PM Pacific Daylight Time,  
dpuopolo at usa.net writes:

I would  guess that your response was either a test to see if I was still
awake, or  not very well thought out!
 
Actually it was a test and you passed one part but failed on another  and 
most have been sleeping on this response:

Also,  there are no 300-ohm windings on a 111-C. The transformer consists of
four  identical windings that are electrostatically shielded so they can  be
connected in any manner. The usual (read correct) connection is for  two
windings to be series-connected for the output, and two windings to  be
series-connected for the output.

Note that both the line-side and  the drop side can be connected
either in series or parallel.   




As Dana points out, the four identical windings are indeed each 300 ohms,  
thus when 2 are connected in series, they present 600 ohms and if 2 are  
connected in parallel, 150 ohms is presented. Indeed the source Z values of  telco 
cable trunks are higher than 150 as you cite. The reason the 150 ohm  
connections are used on each end of the line to be equalized is that the  resulting 
intentional mismatch presents a more gradual rolloff response curve  for the 
equalizer to flatten out as the frequency increases.
 
tm



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