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[TowerTalk] amplifiers for phased arrays

To: <Towertalk@contesting.com>
Subject: [TowerTalk] amplifiers for phased arrays
From: "Dave Bowker" <dbowker@mail.sjv.net>
Date: Fri, 4 Mar 2005 16:44:03 -0500
List-post: <mailto:towertalk@contesting.com>
The performance of any phased array is critically dependent upon proper 
[phasing] and [amplitude] of 
the power delivered to each element in the array.  If we consider only the 
transmitting case, this 
is almost impossible to accomplish with what your are proposing.

The phase from the central feed point to the input of each element amplifier 
can readily be 
controlled, but how do you plan to control the phase shift through each 
amplifier at the element? 
No two power amps exhibit the same phase shift when matched to the load 
impedance ... PERIOD ... 
there are literally an infinite number of L/C combinations which will match the 
amp to the load, but 
each one exhibits a different phase shift.  Amplitude control is possible (at 
great expense of 
complicated circuitry), but each element of a phased array must have precise 
[phase ]AND [amplitude] 
of  power applied to it.

And how do you propose to handle the reverse situation (on receive) ... the 
amps you are 
contemplating ARE NOT BI-DIRECTIONAL !!!

I don't think what you are contemplating is realistic from an engineering point 
of view, let alone 
economics!

73, Dave, K1FK
Fort Kent, ME 


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