I am in the process of phasing two verticals on 160 mtrs. They are spaced
1/2 wavelength apart and my plan is to use a switch box and feed them either
in phase or 180 out.
The alignment of the verticals is such that they are perpendicular to the
shack. To save coax, I came up the ingenius plan to put the switch box
about 6 ft or so from the vertical closest to the house. According to the
MFJ 269, the 3/4 wave feed line is about 266 ft long (RG-213 with V of 66%)
and the antennas are 260 ft apart; so the 3/4 wave line will reach between
the two. I can then coil up both a 1/4 wave line to feed the closest
vertical and a 1/2 wave line to switch in series with the 1/4 wave line.
I have been reading ON4UN's book on Low Band DX'ing, and now am not sure if
this will work. Specifically, section 4.5.1 on page 11-37 talks about
"current-force feeding" and he says; "to preserve symmetry, the T junction
where the lines to the elements join, must be located at the center of the
array".
To do this you have to use two 3/4 wave feed lines for the in-phase pattern
and then a 1/2 wave delay line at the switch box. In my case, this means
another 300 ft or so of coax.
I am not by any means an "antenna expert", but I cannot figure out what
difference it makes whether the switch box (or T) is located in the center
of the array (to preserve symmetry) or at one end. Electrically, it seems
that it makes no difference where the switch box (or T) is. Am I missing
something or does the "physical" symmetry of the "T" or switch box make a
difference?
Thanks for any help on this.
Dick Williams K8ZTT
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