What matters in an array are the relative current amplitudes and phases in
the elements. On a grounded tower, fed with a shunt matching arrangement,
it is possible to measure the net current in the base below the bottom of
the match assembly.
Use a clamp-on current transformer. They are very easy to make and you'll
find examples at www.antennasbyn6lf.com . You have to be careful using
this approach. In the examples I give, I looked at only one
leg of the tower which was fine for that particular experiment. However,
there is no guarantee that two different towers will divide the base current
between the legs in exactly the same ratio so you while you might get the
relative phases right, the amplitude ratios may be off. You may need to
either use core on each leg and sum the currents or put the current
transformer around the connection to the radial system.
73, Rudy N6LF
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