Using transformers to extract the signals from a short antenna will work but
using them in a 4 square would depend on how accurate you would really like to
be in your phasing. There are two issues. Winding a 16 to 1 transformer for RF
is a marginal thing to begin with due to the winding capacitances involved.
Secondly, more important than that is the magnetizing inductance of the 1200
ohm side of the transformer. Normally one would strive for inducive reacance of
10 times the operating load or 12000 ohms in this case when designing a
transformer. If you look at the phase shift of the resulting voltage when fed
with short antenna you will find almost 90 degrees (almost resonant ) which in
itself is not all that bad if all antennas shift the same. This happens even
with the 1200 ohm resistive load reflected from the primary. The problem is
that core material properties vary widely in their single turn inductance
values which in turn from transformer to transformer would be high
ly unpredictable. Especially when fed with an antenna impedance that might
vary a few percent unpredictably (you are only dealing with 75 pf at 160
meters). The real phase shift would be a lot easier to control with a loaded
and tuned element (setting the phase) or having the antenna fed into a high
impedance amplifier ( mostly capacitive input impedance). I did a quick Spice
model of the circuit and changing the magnetizing inductance by as little as 10
percent varied the phase by 7 degrees.
Lee K7TJR Oregon
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