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[Towertalk] Models and real world

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Subject: [Towertalk] Models and real world
From: (Bill Tippett)
Date: Wed, 10 Jul 2002 10:24:10 -0400
W8JI wrote:

>On the other side, they are much closer than we could ever do 
longhand as long as we stay away from limits where they fall apart. 
We have to know the limits of models, just like we have to know the 
limits of measurements. None are perfect, and many are not even 
close. (ie the gain of the antenna is given as 13.65dB but the 
absolute accuracy of the measurement method and instruments is 2dB. 
Why not say "somewhere around 13 dB"?)  

        That's exactly what I said when I first wrote:

        "This should be no surprise.  Even a dipole up 1/2 wavelength
will beat a 4-square.  I recall a dipole's gain is in the order of 2-3 
dB over a 4-square for equivalent grounds.  Add another 4-5 dBd for a 
2 element Yagi and you are around 6-8 dB over a 4-square.  The only 
place a 4-square can realistically compete with a Yagi is if you are
over salt water."

...but then someone wanted to see the model, which confirmed what I 
already stated.  Now someone else questions the model and wants
to go back to the approximations I originally used.  I think I've
just relearned why to never say anything in the first place.  ;-)

                                         73,  Bill  W4ZV  

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