[AMRadio] WTB - MURCH UT-2000A


Paul Christensen w9ac at arrl.net
Sat Jun 12 16:33:35 EDT 2010


> then re-wire it.

I sure would.  To a reversible "L" for use with coax lines -- or a balanced 
version of the L for open lines.

With the classic C-L-C "T" design, multiple panel control settings can 
create an illusion of a low-loss transformation (unless output C is always 
maximized for the given load).  The T is capable of reasonably low loss when 
the L and C components have a Q > 200 and the output C has > 3000-5000 pF of 
maximum capacitance where the connection point to the line is under 25-ohms.

Myself, I cannot imagine using common wire antennas where the feedline Z at 
any point on the transmission line is less than 50-ohms.  That almost always 
indicates an electrically short and inefficient antenna unless extraordinary 
measures are taken at the tuner and antenna to minimize system loss.  Most 
off-the-shelf T tuners suffer great losses with low operating Z.  Unless its 
for mobile use, I really do not want to use antennas that are much less than 
a physical 1/2-wave at the lowest operating frequency.

Paul, W9AC 



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