To: <topband@contesting.com>
>Date: Sun, 3 Nov 1996 14:09:35 -0700
>From: Eric Gustafson <n7cl@sparx.mmsi.com>
>Cc: ham-ant@ucsd.edu, topband@contesting.com
>Reply-To: n7cl@mmsi.com
>
>
>>From: Henry Knoll <Henry.Knoll-1@tc.umn.edu>
To: <topband@contesting.com>
>>Date: Sat, 2 Nov 1996 21:40:13
>>
>>In reading some of the threads which mention radiation resistance
>>of an antenna, I gather the following:
>>
snip...
>
>>It seems that if I know the radiation resistance of the antenna, I
>>can calculate the efficiency--Yes?
>>
>>73 Henry WA0GOZ
>>
>
>Yes.
>
>73, Eric N7CL
>
I relaized after looking at Tom's post that I was thinking in terms of a
simple resonant dipole fed at current maximum. Even the TH7 is
sufficiently more complicated than than so that you would really be reduced
to making (many) field strength measurements of power out of the system
versus feedline measurements of power into the system to determne the
effeciency. But the models will allow you to turn the losses on and off so
that you can get a pretty good idea of the system effeciency. If you
restrict your modeling to free space, and are careful to build the model
carefully, the answers will not be far wrong. The radiation effeciencies
for aluminum yagis (even gain optimized) are quite high in general.
Usually well up into the 90s (percent) without traps.
73, Eric
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