I need some help with phasing two antennas in a stack. The antennas are
Force12 C-3 and C-4XL. The C-4XL is essentially a C-3 with 2-el added for
40M. Since element spacing and feed method (current balun) is the same for
both on 20M, I think I only need to compensate for the difference in
distance of the balun to center of tower between the two antennas. This
distance is 15 inches for the C-3 and 98 inches for the C-4XL. All coax is
Belden 9913F7 which has a velocity factor of 84%.
My first thought was to just make the coax from the C-4XL 83 inches longer,
but now I am not sure. Maybe I need to multiply this by 84%? Then last
night I was reading the ARRL antenna book about phasing different antennas
and got totally confused. Apparently I need to model the two antennas to
find the difference in phase angle in degrees, then add the appropriate
amount of coax to offset the difference. Needless to say, I do not have the
models or experience to do this.
I would appreciate any help in understanding how to properly phase these two
antennas.
73, Keith NM5G
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