[TowerTalk] Phasing Help

[Keith Dutson]

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