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Topband: Modeling W8JI and Hi-Z 8 Circles

Subject: Topband: Modeling W8JI and Hi-Z 8 Circles
From: Dan Maguire via Topband <>
Reply-to: Dan Maguire <>
Date: Sat, 20 Dec 2014 15:39:24 -0800
List-post: <">>
The recent thread on 8 circle arrays prompted me to create a few different 
AutoEZ models, mostly because I was curious about the relationship between 
array size, element phasing, and number of active elements (4 with W8JI, 8 with 

First thing I did was educate myself.  For "W8JI type" arrays:
Low-Band DXing, 4th ed, ON4UN, Chapter 7, Sections 1-21 and 1-30

And for "Hi-Z type" arrays:

Then I created models where the array size (diameter) can be controlled via a 
single variable, along with another variable to control the phasing.  For 
example, here's the AutoEZ Variables sheet tab for a W8JI type array.  The Hi-Z 
is similar except that array size is specified in feet (or meters) rather than 

Since everything is controlled by variables you can run "variable sweeps" 
changing one or more parameters.  Here's the W8JI array with the spacing ("B") 
held constant while the phase delay ("P") is swept from 80 to 140 degrees.  For 
each test case AutoEZ will automatically calculate the RDF (last column).

When the calculations finish you can step through the 2D patterns.  Here are 
the elevation and azimuth (at 20° TOA) patterns for 0.604 wl broadside spacing 
and 125 degree phasing, as shown by "B" and "P" in the lower right corner.

You can run similar sweeps changing the array size while holding the phase 
delay constant, or hold both size and phase constant and do a frequency sweep, 
or use the "Generate Test Cases" button to create any combination.  For 
example, the setup below would vary broadside spacing "B" from 0.50 to 0.70 
wavelengths; for each "B" the phase delay "P" would be varied from 115 to 135 
degrees; all at a constant frequency of 1.85 MHz.  That would be 25 test cases. 
 You can run thousands if you like.

You can also show 3D patterns.  Here's an example of a Hi-Z array, diameter 200 
ft with ±106 degree phasing, along with the 2D elevation pattern.

And here's how the RDF for a 200 ft Hi-Z array varies as the phase is swept 
from ±100 to ±112 degrees.  

For both of the array types, I created one model using W8JI-style top hat 
loaded vertical elements (per the sample model on Tom's site) and a second 
model using simple aluminum tube elements (per the four-section, 23.25 ft, Hi-Z 
AL-24).  Here are the models.  Save to your computer then use the AutoEZ "Open 
Model File" button.

Please note that these models have not been reviewed or approved by the authors 
of the references cited above.  Any mistakes or misinterpretations are strictly 
mine.  And the models may or may not be an accurate representation of any given 
commercial package.

In all the models, a single variable ("X") controls the segmentation.  You can 
reduce that to speed up the calculations.  You can also run a sweep on "X" to 
do a convergence test for model accuracy.

For comparison with the 8 circle arrays, here's the W8WWV "Benchmark Beverage" 
model.  With this one you can "sweep" the length and/or other parameters.

Greg's Beverage page for reference.

Calculated results for this Beverage are shown in section "Calculate 3D Data" 


AutoEZ is an antenna modeling program which uses Microsoft Excel in combination 
with EZNEC.

Current AutoEZ users, see here for recent maintenance updates and instructions 
on how to get the latest release.

Dan, AC6LA
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