YAGIMAX.TXT

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  			YAGIMAX 3.0                      8/91

                     By Lew Gordon, K4VX

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Version 3.0 represents a complete revision of YAGIMAX from previous
versions. YAGIMAX has now been available for about one year and was due
for a "facelift". This new version allows the use of a mouse as well 
as <ALT> and "hot keys" for pull down menus such as are used in 
Microsoft's Word. Pull down help screens are available to assist the 
new user. Version 3.0 is approximately 60 percent faster than all 
previous versions due to the use of the Microsoft (R) Pro-Dev BASIC 
compiler. The use of a Microsoft (R) Mouse (or compatible) is 
recommended with version 3.0. Algorithms remain unchanged from 
versions 2.16 to 3.10.
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The YAGIMAX program represents my latest attempt at antenna modeling 
software. It is based upon the assumption that the antenna is 
monotapered. The algorithm used for YAGIMAX is not derived from MININEC
as was the case with all versions of YAGINEC, but is based upon the
sumption that correctly designed Yagi antennas have a sinusodial 
current distribution which is well behaved. For correct results this 
requires that the user input realistic dimensions when using YAGIMAX.

If you are a previous user of YAGINEC, the first thing you will 
observe is that YAGIMAX is exceedingly fast compared to YAGINEC.
This is a result that the elements are not segmentized and
massaged through Gaussian elimination with partial pivioting matrix 
inversion techniques (the real time consumer in YAGINEC/MININEC), 
but derived from the sinusodial current assumption mentioned above.

To calculate the performance of an antenna using tapered element 
construction, the TAPER program must be used to determine the
monotaper equivalent lengths of each element. A file can be created
by TAPER to transport the dimensions to YAGIMAX. The latest version
of TAPER is 7.07 which is a complete revision from previous versions.
TAPER 7.07 allows importing Yagi Optimizer files (YO) as well as
YAGIMAX files. Both the original W2PV algorithm and the modified
W2PV algorithm are available as well as the W6QHS mounting plate
compensation algorithm. YAGIMAX files can be used to create a YO
tapered file and conversely.

Where YAGINEC will allow the user to model interlaced elements for
several bands (up to a maximum of ten elements), YAGIMAX will not 
provide as accurate results. This is because the current distribution 
on an element somewhat longer, or shorter, than one half wavelength 
will not have exact sinusoidal current distribution. With this in mind, 
the computed performance of a Yagi over +/- 20 percent from its resonant 
frequency may be inaccurate using YAGIMAX.

The maximizing feature is not perfect, but can be used on an element
by element basis to maximize either forward gain, or front to back.
Each element change is cycled through the algorithm three times to
provide a glimpse of what the VSWR is doing at preselected low and
high frequencies. Each change is displayed on the screen for the user
to observe. In many cases the user may want to check the list and
manually re-enter a chosen dimension rather than accept the maximizing
output. There will be some cases where a "runaway" optimization will
occur. This can be halted by pressing the escape key. This can occur
with two or three element designs.

Although it is included as a choice for maximizing, the driven element's 
length should never be used for optimization as it really has very little 
effect upon a Yagis performance except for feedpoint impedance. Also 
2 and 3 element Yagis can display some rather unusual (and unusable) 
results when optimizing for forward gain using spacing adjustments. The 
feedpoint impedance can proceed to values less than one ohm! YAGIMAX only
calculates directivity, not true gain which must include losses. The 
efficiencies of these very low feedpoint designs becomes very low.

The results of YAGIMAX appear to be within 0.3 percent of those 
obtained with NEC2 using ten segments or more for calculation. 
The speed of YAGIMAX is about 50 times faster than YAGINEC using
8 segments per element. As with YAGINEC the more elements in the 
antenna, the slower the calculations.

YAGIMAX will run in systems without a math co-processor but as with
any math intensive program, much slower. A 33 element Yagi requires
several minutes per frequency step using an 8 mHz machine with no 
co-processor. The same antenna on a 20 mHz 80386 Gateway 2000 with
an Intel 80387 co-processor performs 21 steps in 78 seconds. It even
runs 2.5 times faster on machines using the new Cyrix FastMath 
co-processor. 

YAGIMAX 1.03 was the first general release of this program. As with 
all my programming efforts, YAGIMAX is placed in the public domain. 
It is not to be sold or used for commercial gain. While I have made 
every effort to reduce bugs or other problems, I will not be 
responsible for any problems encountered from using YAGIMAX. 

VSWR plot will allow the user to move a frequency flag over the 
plotted curve by using the UP/DN cursor keys. The frequency 
represented by the cursor is displayed in the upper right
hand corner.

The "VIEW" of the Yagi shows the center of gravity (CG) of the 
antenna.It assumes that all elements weigh the same and the boom 
is uniform along it's length. The CG dimension is measured from
the reflector end.

Linear plotting of the results of Gain, F/B, and VSWR vs. frequency
is provided. Those not familiar with the Smith Chart may find this 
display more conventional and  understandable. However, if "off the
wall"  frequency steps are selected, you may get an "off the wall"
display! 

E and H plane plotting in both free space and over perfect
ground is provided. The algorithm used does not calculate the effect 
of mutual coupling between the stacked antennas, but assumes they 
are stacked sufficiently far apart to have minimal aperature overlap 
and mutual interreaction. The high angle lobes will be much lower in 
magnitude in actual practice over real earth as the reflection
coefficient over real ground at the high angles drops drastically.

Free space plotting of stacked Yagis in both polar and linear forms 
uses array factor for the antenna based upon uniform spacing. 
This feature allows inspection of the sidelobe levels of stacked 
arrays for VHF/UHF applications in moonbounce, or where reduction 
in the noise pickup from the sidelobes is critical. When using free 
space H-plane stacking to examine the the sidelobe levels, a -13 dB 
line may be toggled on and off by pressing <Z>. The -13 dB level 
is the accepted point at which maximum stacking gain can be 
achieved commensurate with sidelobe reduction. 

The LINEAR plotting screen can be redimensioned to plot +/-  30 
degrees to provide close-in examination of the immediate sidelobe 
level. This feature is useful when plotting many element stacked 
arrays in free space. Simply press <S> to toggle the scale from 
+/- 180 to +/- 30 degrees scale.

With version 3.08 a "quasi" three dimensional plot is provided
to EGA and VGA users. This feature allows a simultaneous view
of both the E and H planes to inspect for "rabbit ear" side and 
back lobes in the pattern at angles other than zero and 90 degrees.

The Design Scale radius scaling algorithm described in Lawson's 
Yagi Antenna Design pages 7-3 to 7-5 is used to provide an accurate 
method of transferring the design of Yagi from one frequency to 
another. 

Versions beginning with 2.16 incorporate an empirically derived 
algorithm to compensate for the frequency descrepancy between 
NEC2 and YAGIMAX which occurs for large diameter/wavelength elements 
such as are used in VHF/UHF Yagis. Actual NEC runs of several antennas 
with varying element diameters were made and compared to YAGIMAX. 
A second order correction to the self-impedance algorithm in YAGIMAX 
was then made to compensate for the descrepancy. YAGIMAX now tracks
NEC2 results very closely. 
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The included .INP files SUPER10, SUPER15, and SUPER20 are the result 
of stumbling on to an almost perfect Yagi design by continually 
playing with the maximizing feature of YAGIMAX. I wish I had recorded 
each step so a proceedure could be developed, but by the time I arrived 
at the design I had no idea which order of maximizing I had used. I 
plan to revise my current 6 element 15M Yagi which is at 170 feet to 
this design this fall (1991). Try it you'll like it!
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I have written a program NECPLOT which creates NEC input files from 
YAGIMAX .INP files. In addition, the program plots graphically the 
resulting output files from NEC. For those who have access to NEC2 
and wish a copy of NECPLOT send $5 to address below to cover my
expense in mailing.
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All programs on this disk(s) were compiled by Microsoft (R) Basic 
Professional Development System Version 7.0. This compiler generates 
code that runs about 60 percent faster and is 25 percent smaller than 
QuickBASIC 4.5. The programs were written on a Gateway 2000 80386/387 
with color VGA and 8MB of RAM operating under MS-DOS 5.0.
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General tips:

To generate data for a 2 element Yagi where a director is used, simply
enter the director length as a reflector and then place the driven
element behind the director by entering the spacing as a negative number
as in the example below:

  Reflector             31.000                0             0.8750
  Driven element        33.000          -9.5000             0.8750    
 
The numbers will come out correctly.

For a reliable <PRT SCREEN> copy of graphics data insure that the 
transient and stay resident (TSR) program GRAPHICS.COM, which should be
located either in your DOS sub-directory, or on one of your original 
MS-DOS system floppy disks, has been loaded prior to loading YAGIMAX. 
I load it from my AUTOEXEC.BAT file at startup.

EGA/VGA monitors will probably require the monochrome graphics to allow
<PRT SCREEN> to operate correctly. The color versions are much
nicer to look at on the CRT, however. Changing from color to monochrome
can be done at anytime by selecting the menu "Monitor".

As of March 1, 1991, I have some new hope for Hercules Graphic
users. The utilities on this disk SIMCGA.COM, SETCGA.COM, and 
GRABBER.COM were sent to me by my good friend and antenna expert 
Dick Bird, G4ZU/F6IDC. If you are using the HGA card type START and 
the START batch file will load all of the necessary files into 
memory for simulating CGA on almost any machine (even those with no 
graphics card I am told!). Graphics hard copy can be helped by using 
GRABBER.COM. If you read French, the documentation is on the 
disk. As I do not have access to a Hercules graphics computer
I cannot directly verify the above. You are on your own!

Some users of EGA have encountered problems using <PRT SCR> to
make a hard copy. It appears that placing the file EGAGRAF.COM 
(included on this disk) in your AUTOEXEC.BAT file may clear up 
this anomaly. The circles may come out somewhat eliptical, but 
this also can usually be corrected in most modern printers using 
a macro to reduce/increase line spacing prior to printing.
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I have included the Yagi design program DL6WU-2 with my programs. 
This program is based upon the results obtained by DL6WU
from actual antenna range testing of Yagis. Although it is empirically
derived, the results are quite close to those obtained by using
mathematical modelling such as YAGIMAX. It is particularly useful 
for VHF/UHF long boom designs. The algorithms and original interpretive 
BASIC program DL6WU-1.BAS were produced by KY4Z and W6NBI. The version
DL6WU-2 is my compiled version of the same program.
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As of July 1, 1991, the programs HAIRPIN, GAMMA, and GAMMA2, are
no longer included with YAGIMAX. Instead I have combined all three
programs into a single program MATCH. In addition, MATCH contains 
an algorithm for calculating the feed point impedance for folded 
dipoles with unequal element diameters for VHFers.
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Ken Wolff, K1EA, encloses following humorous paragraph with his CT 
contest program which says it all! I share it with the user.

   "Engineering (me) is very upset with Quality Assurance (me). Marketing
has demanded a corporate Quality Awareness Program and sales is out in a
bar drinking somewhere. Our CEO (me) has appointed a new Director of
Corporate Quality and Customer Relations (me). We will be holding the
first of our Quality Tiger Team meetings next week in preparation for
a Quality Audit Week. Each of the developers and code auditors will be
asked to prepare a Quality Improvement Plan. After all this important
stuff is out of the way, I hope to have time to look at the code a
little more carefully."

Thanks Ken, I needed that! 
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If you received your copy of YAGIMAX from a shareware dealer, or 
someone else other than me, or via a BBS, you must send your $8.00 
donation to the address below or your concience will bother you forever!

If you enjoy these programs don't hesitate to send your cards and letters
(& donations!) to the following address:

Lew Gordon, K4VX
P.O. Box 105
Hannibal, MO 63401
(314) 221-7730
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