I queries WX0B about the rule of thumb regarding "optimum" stacking
height.
Here was his response:
***********************************
For HF antennas over ground, W2PV did the math correctly and the
formula is SQ rt of boom length is the widest stacking distance you
should use on a yagi. The results are in boom lengths just as you
state.
Also a model should be run to verify no strange pattern lobes are
created in the stack.
***********************************
Note the origin was not via emperical results but is based in
mathematics.
The fact that one can do detailed analytical calcs that in many cases
agree with this "rule of thumb" support its use as an intial point for
optimization studies.
Clearly the "bad lobes" one is trying to squish into desirable lobes
is a function of antenna height. The variables of stack spacing an
antenna phasing are the only things left to play with after the top
antenna height is fixed. No doubt there optimum spacings which
deviate from the rule of thumb.
We are so fortunate to have tools available to do the design fine
tuning.
I can't imagine one spending kilobucks on a stack and not modeling
them with these tools.
73 de Brian/K3KO
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