[TowerTalk] Stacking order & spacing

Mark Beckwith n5ot at n5ot.com
Thu Aug 24 06:58:39 EDT 2006

Barry, W1HFN asked:

> 1.  What is the optimal stacking order, from tower top to top of mast?
> I assume the rotary dipole, then TA-33, then 2M beam.

Barry, some of your questions may be answered by the strength of your mast 
and the windload capacity of your rotator.  Should we assume the tower will 
be guyed?  If it was me, I'd probably put the 2M antenna at the top, then 
the rotary dipole then the tribander at the top of the tower.  I would not 
separate the top two antennas by a lot, but I'd try to get as much distance 
between the two HF antennas, both to reduce interaction and to get the 
rotary dipole with 40M as high as possible.

Personally I don't like having antennas on a mast that point in different 
directions because that inevitably bites me in the butt when I'm operating. 
However, turning the rotary dipole 90 degrees to the tribander would 
probably result in less interaction between the two HF antennas, and could 
result in a lower max windload of the configuration (not a foregone 
conclusion, however, you should calculate it and see).

It is possible that the configuration with the greatest loads might still 
not exceed your tower, mast and rotator load limits, in which case higher is 
better and all antennas pointing the same way is better.

Final caveat: Don't take the strength of the mast for granted.  Experience 
shows cutting corners on the mast is frequently a false economy and/or 
dangerous.  You should figure out the loads and use something that will do 
the job, or if you already have the mast, work it backwards to figure out 
how high you can safely mount the antennas in what configuration.  Bear in 
mind that sometimes the best way to get the higher antennas on there is to 
climb the mast, so it has to take all that abuse too :)

Mark, N5OT 

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