[TowerTalk] Coax lengths for phasing a stack

[Grant Saviers]

I'm ruminating about what lengths I need for 5L over 5L stacks to 
equalize the antenna feedpoint phase.  The literature seems thin and the 
common answer is "make the feed-lines the same length", which I am 
certain will work.

However, when the stack separations are sufficient, there may be more 
than 1 wavelength of coax needed to equalize the lengths.  e.g. 60' 
separation on 20m at 0.89 vf (LDF5) is just about 1 wl.  It seems to me 
there is little downside with ham radio modulation systems to phase at 0 
(equal lengths) or +/- n * 360 degrees (where n is 1 or 2).  Perhaps 
some cw waveshaped attack/decay envelopes will change a tiny bit, but 
that seems like a slight downside.

So it may work out that no extra phasing line is needed for certain 
separations.  I am planning that all misc lengths of coax's and types 
are the same for both antennas (rotator loops, boom and choke lengths).

Then there is the slightly counter-intuitive result that making the 
longer (higher antenna) feedline a bit longer minimizes the coax used in 
the phasing at some separations.  And one more trick would be to reverse 
the outputs of one side of the TLT matching transformer for BIP to 
eliminate 1/2 wl of phasing line.  It wouldn't matter for Top or Bottom 
only use.

So, is this analysis correct?  Any other options for using less coax?

Grant KZ1W