[TenTec] Re: Rudimentary SWR question...

K3BU at aol.com K3BU at aol.com
Thu Oct 23 22:29:35 EDT 2003

In a message dated 10/23/03 6:49:29 PM Eastern Daylight Time, 
rohre at arlut.utexas.edu writes:
No one uses an untuned mobile whip, who desires to get the most power to the
antenna and radiated.   As in any non resonant antenna system,  once you use
the tuner, you have matched (canceled the antenna reactance) and you are
resonant everywhere in the system.  This is covered well in Maxwell's
original QST papers and in his revisions, "Reflections II" which is
available thru "World Radio" bookstore.

The losses in a good tuner and short transmission line in the mobile case,
are a pretty small part of efficiency.  It is still possible to get near
resonant dipole efficiency, if your other losses are minimized and you
complete the mobile whip with a good radial system. 

Not that simple. 
The worst efficiency for shortened or mobile antennas is obtained with base 
loading coil or tuners at the base of the whip. Major "fight" about the 
distribution of the current in the loading coils and significance of positioning of 
the loading coil in the antenna is at eHam.net and article

and complete article with photos is at my page

In short, efficiency of the loaded antenna is roughly proportional to the 
area under the current curve and position of the loading coil has significant 
role in it.

Yuri, K3BU

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