My 42' tower and SteppIR 3 element beam at 45' are shunt fed at the thrust
bearing. A single 120' horizontal loading wire is also attached to the thrust
Very clearly, tuning the elements of the SteppIR effectively changes the
feedpoint impedance of the tower on 160M. Even though the SteppIR elements are
electrically 'floating' above the boom, changing their length does change the
feedpoint. The 20M position on the SteppIR places the 'sweet spot' at about
1825. The 15M position places the sweet spot at about 1860. Retracting the
elements completely is not useful as the 'effect' of the elements is nil once
retracted to the 10M position or so.
While the system is far from ideal for a number of reasons, it does work. And
the configuration illustrates that the 'loading' can take place in spots other
than the top of the vertical, which in my case is an inverted L arrangement.
It is apparent to me that I do not fully understand the workings of the
system--discovered using serendipitous methods. A similar stunt is performed
on 80M using a separate shunt (tap at 33' instead of 42') and a horizontal hat
wire of only 20', but the position of the SteppIR elements has no effect on
feedpoint impedance on 80M. Go figure...
Your mileage WILL vary...
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