Feeding Antennas w/ Sep Amps

[Steve Fraasch]

Far be it from me or anyone I know to feed antennas with discrete amplifiers...
.......or judge those who are serious,

but.....

IF SOME FOREIGN AMATEUR, or U.S ham who is slightly possessed were interested, 
he would need to concern himself and become fluent with array theory.  The 
drive conditions at each antenna would not only depend on the self drive 
impedances, mutual coupling effects between antennas, & transmission line 
lengths, but also the relative amplitude and phases of each amplifier.  Far-
field antenna patterns are derived from the summation of antenna currents 
operating on a Green's function for that object and others in the near field (
ground, trees, towers, guys, other antennas).  Only the antenna currents - 
nothing else - matters.  Adding new sources changes the current distribution, 
but how will you know how?

In other words, a haphazard arrangement of discrete amps and antennas would 
probably result in an effect opposite that which was desired: a big, fat, 
bulbous, non-directive pattern.  More importantly, the receive array 
performance would be grossly different than the transmit performance (the 
amplifiers change feed point drive conditions during transmit, that they won't 
affect during receive).

At work, we've attempted to feed FM/CW radar antenna arrays with separate 
transmitters & receivers.  You will gain an appreciation for the IMMENSE 
difficulty in trying a multiple source technique if you play similar games.

If you're really interested, you may want to refer to the original:  G. H. 
Brown's paper on vertical arrays (IRE, 1937).  Also, you'll need to pay 
attention to W0UN's comments on how to measure the relative phases and 
amplitudes of each amplifier (which will then be shifted by transmission line 
lengths, and further modified by self drive and mutual impedances).

Did these questions originate from the 48 vs 24 hour contest gang?  To the 
sick and perverted individuals actually serious in doing this,

Good Luck!                              Steve, K0SF

P.S> I assume you're not a qrp op.