[TowerTalk] How can a SteppIR Perform So Well?
Joe Subich, K4IK
k4ik at subich.com
Thu Mar 17 11:47:03 EST 2005
> I think the point I was trying to make was... if a well
> designed yagi with 4 elements works as well as a well designed
> 5, 6 ... element yagi, then why would anyone want to purchase,
> buy, or build the larger antenna?
The key is in what you mean by "performs as well." If the only
concern is gain at a specific frequency, then the four element
antenna will perform just as well as a five, six or more element
antenna on a boom up to about 3/4 wavelength. If your concerns
include SWR, F/R and bandwidth, the design flexibility provided
by the additional fixed length elements will allow the antenna
with the "extra" elements to outperform the four element design.
However, if you remove the constraint of fixed length elements
and bandwidth, the four element antenna again becomes a valid
SteppIR's unique asset is the adjustable (tunable) element.
The three element SteppIR is a valid comparison to your C3 ...
the SteppIR has half the elements on a boom that is two feet
shorter. Yet the SteppIR outperforms the C3 in model studies
and range tests using the K7LXC/N0AX protocols.
> The SteppIR 3 element yagi vs Force 12 C-3E (74' above ground)
> C-3E SteppIR elev.
> Band Gain F/R Gain F/R
> 20 12.6 16 13.4 20 13 degrees
> 17 10.3 7 13.8 21 10 degrees
> 15 12.8 17 14.2 21 8 degrees
> 12 9.8 9 14.8 14.5 7 degrees
> 10 13.2 21 15.2 11 7 degrees
> 6 n/a 16.0 20 4 degrees
> The C-3E numbers are Force-12 published specifications and
> confirmed by modeling with AO. The SteppIR numbers are from
> modeling in AO/YO (6 meter values use the optional passive
... Joe, K4IK
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