EZNEC Antenna Modeling Software Prepared for the Rappahannock

EZNEC Antenna Modeling Software Prepared for the Rappahannock Valley Amateur Radio Club Meeting, Aug 22, 2017 By David P Head K 8 DH

EZNEC is a software program “wrapper” for the NEC-2 antenna modeling software suite. It makes entering data used by the NEC-2 modeling software more straightforward than working with NEC-2 software directly.

NEC is an acronym for Numerical Electromagnetics Code Original program was BRACT was built in the early 1970’s.

BRACT • Modeled aircraft and satellite antennas • Did not model effects of the ground • Written by MBA Associates for USAF’s Space and Missile System’s Center

AMP • Next iteration of antenna modeling software built on BRACT • Also written by MBA Associates • Created to account for ground

AMP 2 • Follow-on to AMP • Written by programmers at Lawrence Livermore National Laboratories • Written for Naval Ocean Systems Center and Air Force Weapons Laboratory

NEC 2, 3, & 4 • Iterations with increasing refinements and capabilities • NEC-4 has new licensing scheme and is not open source

NEC Was Text Based Example input file for a 12 element log periodic antenna: CM TESTEX 5 CM 12 ELEMENT LOG PERIODIC ANTENNA IN FREE SPACE CM 78 SEGMENTS. SIGMA=O/L RECEIVING AND TRANS. PATTERNS. CM DIPOLE LENGTH TO DIAMETER RATIO=150. CE TAU=0. 93. SIGMA=0. 70. BOOM IMPEDANCE=50. OHMS. GW 1 5 0. 0000 -1. 0000 0. 00000 1. 0000 0. 00667 GW 2 5 -. 7527 -1. 0753 0. -. 7527 1. 0753 0. . 00717 GW 3 5 -1. 562 -1. 1562 0. -1. 562 1. 1562 0. . 00771 GW 4 5 -2. 4323 -1. 2432 0. -2. 4323 1. 2432 0. . 00829 GW 5 5 -3. 368 -1. 3368 0. -3. 368 1. 3368 0. . 00891 GW 6 7 -4. 3742 -1. 4374 0. -4. 3742 1. 4374 0. . 00958 GW 7 7 -5. 4562 -1. 5456 0. -5. 4562 1. 5456 0. . 0103 GW 8 7 -6. 6195 -1. 6619 0. -6. 6195 1. 6619 0. . 01108 GW 9 7 -7. 8705 -1. 787 0. -7. 8705 1. 787 0. . 01191 GW 10 7 -9. 2156 -1. 9215 0. -9. 2156 1. 9215 0. . 01281 GW 11 9 -10. 6619 -2. 0662 0. -10. 6619 2. 0662 0. . 01377 GW 12 9 -12. 2171 -2. 2217 0. -12. 2171 2. 2217 0. . 01481 GE FR 0 0 46. 29 0. TL 1 3 2 3 -50. TL 2 3 3 3 -50. TL 3 3 4 3 -50. TL 4 3 5 3 -50. TL 5 3 6 4 -50. TL 6 4 7 4 -50. TL 7 4 8 4 -50. TL 8 4 9 4 -50. TL 9 4 10 4 -50. TL 10 4 11 5 -50. TL 11 5 12 5 -50. , . 02

EZNEC Interface

EZNEC Author Roy Lewallen

Several Versions with Different Prices • Free Download, limited to 20 segments (can’t do much but eval the interface) • EZNEC V. 6. 0 – Useful program with NEC-2 engine, $99 • EZNEC+ V. 6. 0 – More useful program with NEC-2 engine, $149 • EZNEC Pro 2 v. 6. 0 – Professional model with NEC-2 engine $525 • EZNEC Pro 4 v. 6. 0 – Professional model with NEC-4 engine $675

EZNEC v. 6. 0 and EZNEC+ v. 6. 0 Are Most Useful for Us • Reasonably priced at $99 and $149 • Standard has 500 segments, Plus has 2000 • Plus Imports wire coordinates in CSV files • Plus has additional wire manipulation features

CAUTION – ADDICTIVE! • The enemy of good, all-night sleep is not video games, it is EZNEC! • Daydreaming may occur: “I wonder if I should model the metal supports, ” and “What is the best height for my antenna? ”

LAST. EZ Makes Returning to Your Previous Work Easy

Write Your Filename to Identify What LAST. EZ Was Derived From

Left Controls Call Up Information

Right Controls Let You Change Things

Src Dat Button -> Source Data Display

SWR Button -> SWR Sweep Parameters

SWR Run Results Note Custom 200 Ohm Impedance

VIEW ANT -> Antenna Display 3 3 -Element Yagis Ganged Side-By-Side

FF Plot –> Far Field Plot, 2 D, Azimuth

FF Plot -> Far Field Plot, 2 D, Elevation

FF Plot -> Far Field Plot, 3 D

Right Controls Let You Change Things

Right Side Buttons With Chevrons Allow Adjustments • Frequency Button allows setting frequency • Wires button provides a grid to define end points and ‘wire’ sizes, where wires can be tubing • Sources allow placing of sources on specific wires • Loads allow placing of loads • Trans Lines allows connection of transmission lines • Transformers allows insertion of transformers

Right Side Buttons (Cont’d) • L Networks Allows Insertion of L Networks • Ground Type offers predefined ground types as well as customized types • Ground Descrip appears to allow concentric sections of ground with different elevations, radii and conductivity. The dialog is labeled “Media” • Wire Loss allows you to define perfect, copper, aluminum, tin & zinc, as well as custom parameters

Right Side Buttons (Cont’d) • Units allows Meters, Millimeters, Feet, Inches, and Wavelengths selection allows wires to be defined in Millimeters, Inches, & Wavelengths. • Plot Type allows the FF Plot to be selected for Azimuth, Elevation, and 3 D • Elevation Angle / Azimuth Angle allows setting these parameters for the Azimuth and Elevation Plots

Right Side Buttons (Cont’d) • Azimuth / Elevation Angle button disappears when 3 D plot type is selected • Step Size allows selection of how many degrees between calculations around the plot display. Smaller step size may yield greater accuracy • Ref Level defaults to 0 dbi. • Alt SWR Z 0 lets you select a different impedance • Desc Options gives description selection options

Wires Button -> Wires Dialog • Wires dialog shows the wires for 3 3 element 20 meter yagis ganged side-by-side, with triply folded dipole driven elements. • Wires 1, 10, and 19 are directors • Wires 5, 14, and 23 are driven elements • Wires 9, 18, and 27 are reflectors • Wires 2, 3, 7, 8, 11, 12, 16, 17, 20, 21, 25, and 26 are end connectors for the folded dipole driven elements. • Wires 4, 6, 13, 15, 22, and 24 are the folded dipole “folds. ” • X, Y, and Z are Cartesian Coordinates • Z is the height above ground in feet • “Conn” column defines connections between wire ends

3 3 -Element Yagis Ganged Side-By-Side Overhead View With Wires With Numbers • Thicker Driven Elements are Triply Folded Dipoles

Why Folded Dipoles? • Driven elements of the 3 element yagis are around 25 – 30 ohms • Folded dipoles have higher impedance that are multiples of the square of the number of wires in the folded dipole • Triply folded dipoles, then, have their impedance multiplied by 9.

Folded Dipoles (Cont’d) • The Src Dat button gives us the result: • Note the 3 sources for the 3 different driven elements are 271. 2, 233. 4, and 271. 2 ohms. • Native, non-folded driven elements would have been 30. 13, 25. 93, and 30. 13 ohms. • Also note the reactance of –J 0. 9584, -J 0. 1432, and –J 0. 9599 ohms. This means effectively these driven elements are resonant at the selected 14. 175 Mhz frequency. • Interesting too is that the center yagi of the 3 ganged yagis has a lower impedance than the 2 end yagis. • Also true is that the driven element of the center yagis had to be made slightly different in length to get J to near zero (achieve resonance. )

Folded Dipoles (Cont’d) • The Src Dat button gives us the result: • Note the 3 sources for the 3 different driven elements are 271. 2, 233. 4, and 271. 2 ohms. • Native, non-folded driven elements would have been 30. 13, 25. 93, and 30. 13 ohms. • Also note the reactance of –J 0. 9584, -J 0. 1432, and –J 0. 9599 ohms. This means effectively these driven elements are resonant at the selected 14. 175 Mhz frequency. • Interesting too is that the center yagi of the 3 ganged yagis has a lower impedance than the 2 end yagis. • Also true is that the driven element of the center yagis had to be made slightly different in length to get J to near zero (achieve resonance. )

Folded Dipoles (Cont’d) • The Src Dat button gives us the result: • Note the 3 sources for the 3 different driven elements are 271. 2, 233. 4, and 271. 2 ohms. • Native, non-folded driven elements would have been 30. 13, 25. 93, and 30. 13 ohms. • Also note the reactance of –J 0. 9584, -J 0. 1432, and –J 0. 9599 ohms. This means effectively these driven elements are resonant at the selected 14. 175 MHz frequency. • Interesting too is that the center yagi of the 3 ganged yagis has a lower impedance than the 2 end yagis. • Also true is that the driven element of the center yagis had to be made slightly different in length to get J to near zero (achieve resonance. )

Folded Dipoles (Cont’d) • The Src Dat button gives us the result: • Note the 3 sources for the 3 different driven elements are 271. 2, 233. 4, and 271. 2 ohms. • Native, non-folded driven elements would have been 30. 13, 25. 93, and 30. 13 ohms. • Also note the reactance of –J 0. 9584, -J 0. 1432, and –J 0. 9599 ohms. This means effectively these driven elements are resonant at the selected 14. 175 Mhz frequency. • Interesting too is that the center yagi of the 3 ganged yagis has a lower impedance than the 2 end yagis. • Also true is that the driven element of the center yagis had to be made slightly different in length to get J to near zero (achieve resonance. )

Folded Dipoles (Cont’d) • The Src Dat button gives us the result: • Note the 3 sources for the 3 different driven elements are 271. 2, 233. 4, and 271. 2 ohms. • Native, non-folded driven elements would have been 30. 13, 25. 93, and 30. 13 ohms. • Also note the reactance of –J 0. 9584, -J 0. 1432, and –J 0. 9599 ohms. This means effectively these driven elements are resonant at the selected 14. 175 Mhz frequency. • Interesting too is that the center yagi of the 3 ganged yagis has a lower impedance than the 2 end yagis. • Also true is that the driven element of the center yagis had to be made slightly different in length to get J to near zero (achieve resonance. )

Antenna System has 3 Sources • Talked with Mr. Roy Lewallen at Dayton, who said, “Model your transmission lines, they don’t work like you think. ” • Objective is to get the 3 feedpoints, ranging in the 300 – 400 ohm region, up to 3 600 ohm open wire lines. • Connect the 3 600 ohm lines in parallel to yield a 200 ohm feedpoint for a 4 to 1, 50 to 200 ohm balun

EZNEC Model Of These 3 Sources Would Be Difficult to Measure • ARRL Antenna Book, 23 rd Edition, 24. 4. 3 Series Section Transformers is an answer • Formulas for transforming complex impedances to pure resistive result are given:

I Programmed The Linear Transformer Equations into Excel

Resulting EZNEC Implementation of 3 Linear Transformers • Proper placement of calculated sections of 300 ohm twinline results in 3 600 ohm resistive loads

Result of Combining the 3 600 Ohm Transmission Lines • Impedance Near-Perfect at 199. 9 ohms resistive and –J 1. 342 ohms reactance • SWR referenced to custom 200 ohm system (for connecting the 4 -1 balun) is 1. 007 to 1

Best Reason to Buy the Plus Version ($149) • • Import Wires from Ascii File This means a comma separated values (CSV) file Excel will produce CSV files Excel can easily be programmed to calculate wire parameters

Excel Calcs For The 3 3 -Element Yagis • Just save this as a CSV • Anything after a semicolon is a comment which EZNEC ignores • While EZNEC has many features for manipulating groups of wires, I think attempting to model this would have been much harder without Excel

A Shocking Revelation • Dipole in free space = 2. 11 d. Bi

A Shocking Revelation (Cont’d) • Dipole over “Real / MININEC” ground = 6. 82 d. Bi

So When Anyone Says, “A Dipole Is A Real Working Antenna…” • It is • There are lots of antennas you can put up that won’t perform as well as a dipole • Learning what these underperformers are can be done by spending a lot of time and money building and measuring them, or • You can model them for the price of this software

ARRL Antenna Book CD Supports EZNEC • 388 Modeling Files for Common Antennas

HELP Contains Complete Manual Which is Also Available as a PDF

HELP Contains a Tutorial • Example EZNEC files come with installation and support the tutorial

Just Fooling Around 90 Elements on 20 Meters • 30 3 -element Antennas Side-by-Side • No attempt to simulate a feed system • 1049 feet “wide” • 23. 86 d. Bi compared to 15. 2 d. Bi of the similar 9 element array previously illustrated • 10 X number of elements but not 10 X gain • 3. 6 degree beamwidth impressive • 3. 6 degree beamwidth would require a variable phasing harness to steer the beam • Bill Gates probably couldn’t afford that phasing harness • But its fun to play with this software, which CAN keep you up all night!!!

The End! I hope you enjoyed the presentation Dave Head, K 8 DH