From: rabassa_ao%ncsd.dnet@gte.COM (NW2M reply: rabassa_ao%ncsd.dnet@gte.com)
Newsgroups: rec.radio.amateur.misc
Subject: Antenna Modeling - performance results - YAGIMAX 2.21
Date: 12 Aug 92 13:17:48 GMT
Organization: UCSD Usenet Gateway
NNTP-Posting-Host: ucsd.edu

YAGIMAX ver 2.21 Followup:   Aug/12/92    NW2M
Yagimax was available via its' creator - K4VX, as I did.
The online callbook says:
        K4VX:E:Griffith L Gordon:POB 105:Hannibal:MO:63401

I sent a blank formatted disk, mailer, return postage, and my thanks.
No other fee was expressed at that time (3/91)..... this is 92.....
an election year... need I say more.....
------------------------------------------------------------------------
Performance (386-40Mhz, 64k cache, no math coprocessor, VGA),
5 Element yagi (HyGain model) 20 meter band:

  30 seconds for full freq sweep (45 points - gain, F/B, Imp, SWR).
   3 seconds to compute and display Smith Chart (color vga).
   8 seconds to compute polar plot.
   3 seconds to draw polar plot (color vga).
   3 seconds to draw any other graph/chart (color vga).

VERY fast and VERY impressive.  Please post your findings, the latest
version number, and notes from K4VX (wishes, etc...) to the net.

Any other questions about Yagimax, ARRL "Yagi Antenna Design" book,
antenna modeling, pitfalls, etc., drop me a line.

My original yagimax posting follows:
=======================================================================
.Antenna Modeling Program - YAGIMAX ver 2.21  Shareware Product
.
.I received a shareware copy of Yagimax from the author about a year
.ago.  It was a PC based (clone or otherwise) software package.
.The package fits onto one 5 1/4 disk.  The disk contains the
.Yagimax.exe, Install program, Gamma Match calc program, Taper
.correction program, and several data files (actual models!).
.
.Run the install program 'YMINST.EXE' and answer the video type and color
.selections you prefer.  Instructions are included on the disk README.NOW.
.
.Running the program.  The opening window (not a windows or X product),
.allows the selection for creating a new model or load an old one.
.Selecting LOAD will present a window of existing antenna files.
.Arrow down to your selection and depress enter.  The dimensional
.data (length, width, spacing...) is displayed.  DOS limitations
.allow short filenames - so be brief.  NBS3217.INP would correspond
.to the NBS model at 3.2 wavelengths, 17 elements.  Other filenames
.follow suit.
.
.The program is very easy to follow, and moving around is simple.
.It provides gain, F/B, SWR, and feed point impedances over selected
.frequency start/end points.  You can maximize gain or F/B by element 
.lengths or element placement.  Assuming similar element construction,
.the balance point (CG) is computed and displayed.  Polar plots,
.Smith Charts, Graphs, etc and be displayed. Stacking and height
.above ground results also computed.
.
.I entered the NBS model for 3.2 Lambda, 17 elements for 144 Mhz.  
.The NBS and the Yagimax model numbers are in agreement !! 
.My feed point numbers were 25 -20j  (as an example) at 144.200.
.These numbers are entered into the GAMMA match program, assuming
.a gamma feed system, and the program computes gamma dimensions.
.At 144, no TAPER corrections are needed, but corrections for
.boom effects are computed by the TAPER program.
.
.In summary, a simple and easy program to use.  For HF work, 3 to 5
.elements run quickly on my 286-12MHz VGA clone.  22 element VHF/UHF
.models took forever.  Since then, I have upgraded to a 386 at 40 MHZ
.with 64k cache. Now it flies !!!!  Yagimax also looks for a math 
.co-processor.  
.
.PITFALLS:  Don't get caught in the deadly spiral !!! Especially with
.simple 3 element designs.  Antennas should exhibit smooth gain and swr
.figures.  F/B changes quickly - as expected.  DO NOT try to squeeze 
.the last .00001 dB out of the antenna !!!!!  Models will allow a 100 dB
.gain with 400+ dB F/B for one frequency - but one 1 Hz will result
.in a 500 dB loss in gain and 300 dB loss in F/B and an increase 
.of 100:1 in SWR!     It does not exist !!    Don't fall for it!!!  
.Play it safe.  Use one of the NBS (your tax dollars) models in the ARRL 
.handbook as a starting point and 'touch-up' with modeling from there.
.
.73, and good luck.   Al NW2M  Rockville, MD  (301)294-8621
--------------------------------------------------------------------------------
  |\    |  |      |   -----  |\    /|     Al Rabassa, NW2M   GTE Govt Systems
  | \   |  |      |        | | \  / |                          Rockville, MD
  |  \  |  |  /\  |   -----  |  \/  |                          (310) 294-8621
  |   \ |  | /  \ |  |       |      |
  |    \|  |/    \|  |_____  |      |     Reply:rabassa_ao%ncsd.dnet@gte.com
"Nice Signal...considering I have the back of the beam pointing away from you." 
--------------------------------------------------------------------------------
Newsgroups: rec.radio.amateur.misc