[CQ-Contest] Two Towers, Two Tribanders - Coax Length for Stack Match?

David Pruett k8cc at comcast.net
Sun Jul 12 13:27:30 EDT 2015


As I am sure you are aware, if the two antennas/arrays are in phase the field strengths add and if out of phase subtract.  Feed line length is only half of the question in regards to phase.  The distance between the towers, the direction of interest and relative positions of the towers in azimuth have just as much effect.

If the antennas have good directivity and are pointed in different directions where the patterns don't overlap, then none of this really matters.

I do a lot of multi-direction spraying at K8CC, but how I do it differs.  I have a 2-stack on 20M plus a fixed SE yagi on another tower, a 3-stack on 15M plus a fixed SE yagi, but on 10M I just have  3-stack.  In a DX contest where I might try to spray towards different continents and I'm concerned about phase I just use the stack aimed in different directions.  But in SS where I like to spray everywhere I'll aim the stacks W/NW and SW and on 20M/15M I'll rig up an uneven power splitter with some coax and add the fixed SE into the system. (I use an uneven split to ensure most of the power goes to the stack, which is aimed in the primary direction of interest.). On 10M where I don't have a fixed SE yagi, I just spray the 3-stack NW/SW/SE.  It all works very well.

73, Dave/K8CC

Sent from my iPhone

> On Jul 12, 2015, at 8:14 AM, Richard Thorne <rthorne at rthorne.net> wrote:
> I'm in the process of putting up a second tower which will have stacked tribanders.  These 3 tribanders will be fed via a Stack Match with equal lengths of coax.
> My current tower also has a tribander.
> I plan on installing a stackmatch II switch between the two towers for quick direction changing or spraying my signal in 2 directions.
> Is it worth the trouble to use equal length feed lines?  If I use what I currently have one feed line will be 278' and the other will be 140'.
> Thanks
> Rich - N5ZC
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