The W8IO Antenna Site - NEC and Mininec

(14 March 2022)

Russia began a full-scale invasion of Ukraine on 24 February 2022, in an escalation of the Russo-Ukrainian War that began in 2014. The invasion is the largest conventional military attack on a sovereign state in Europe since World War II. Since the beginning of Putin's war, thousands of both Ukraine and Russian citizens have been killed. Russian military have indiscriminately bombed cities in Ukraine, destroying many hospitals and schools. Our heart goes out to the 2.7 million plus refugees that have left Ukraine for neighboring countries, and those who stayed to fight the Russian invaders.

Rossiya nachala polnomasshtabnoye vtorzheniye v Ukrainu 24 fevralya 2022 goda v ramkakh eskalatsii rossiysko-ukrainskoy voyny, nachavsheysya v 2014 godu. Eto vtorzheniye 
yavlyayetsya krupneyshim voyennym napadeniyem s primeneniyem obychnykh vooruzheniy na suverennoye gosudarstvo v Yevrope so vremen Vtoroy mirovoy voyny. S nachala putinskoy 
voyny pogibli tysyachi grazhdan Ukrainy i Rossii. Rossiyskiye voyennyye bez razbora bombili goroda Ukrainy, unichtozhiv mnozhestvo bol'nits i shkol. My sochuvstvuyem boleye 
chem 2,7 millionam bezhentsev, pokinuvshikh Ukrainu v sosedniye strany, i tem, kto ostalsya srazhat'sya s rossiyskimi okkupantami.

Россия начала полномасштабное вторжение в Украину 24 февраля 2022 года в рамках эскалации российско-украинской войны, начавшейся в 2014 году. Это вторжение является крупнейшим 
военным нападением с применением обычных вооружений на суверенное государство в Европе со времен Второй мировой войны. С начала путинской войны погибли тысячи граждан Украины 
и России. Российские военные без разбора бомбили города Украины, уничтожив множество больниц и школ. Мы сочувствуем более чем 2,7 миллионам беженцев, покинувших Украину в 
соседние страны, и тем, кто остался сражаться с российскими оккупантами.

NEC Software for Yagi Design

Note: K6STI's AO and YO software no longer available. His older versions will not work in Windows 7 and 8.

NEC/MININEC-based Software Vendors:

• EM Scientific: "New" MININEC  Free "Expert MININEC Classic" software - bad link?

• EZNEC/EZNEC+ and EZNEC Pro (W7EL)

• NEC-Win Plus, NEC-Win Pro, GNEC "Nittany Scientific" - now out of business

• Orion Microsytems: NEC4WIN MININEC Software "NEC4WIN95" - do not order from KAGI?

• Super NEC "SuperNEC" NEC2/UTD combo

• 4NEC2  Free NEC-2 software with excellent GUI - new web site: qsl.net/4nec2

• NEC2++  from Tim Molteno (discussion forum)

• AutoEZ, TLDetails & MoxGen  by Dan Maguire AC6LA

• MMANA Free software based on MININEC from DL2KQ-EU1TT

• CocoaNEC Free NEC software for the Mac OS-X Tiger operating system by W7AY

Other MOM-based Software Providers:

• WIPL-D Method of Moments software

• ANSYS Designer  2D+ Code for Patch Antenna Design (Free Student Version - no longer available)

• Mentor Graphics Software (was IE3D)  2D+ Code for Patch Antenna Design

• Antenna Design Freeware  from Meyers Engineering

• MOMIC Method of Moments Interactive Code - not available?

• NEC-BSC NEC Basic Scattering Code, ESP -Electromagnetic Surface Patch Code and others(Ohio State)

• YagiCAD 6.2.0 free Yagi-specific Windows software by VK3DIP

• Yagi Modeler Applet online applet to simulate Yagis by W9CF

• More software?

FEA-based Software Vendors:

• ANSYS HFSS 3D Antenna Structure Simulator

Antenna Structural Analysis Software:

• YagiStress

NEC/MININEC Organizations and Resources:

• The Applied Computational Electromagnetics Society (ACES)

• The (Unofficial) NEC Archives (WB6TPU) Free Software!

• NEC-2 information Users Manual for NEC and other information

• L.B. Cebik's Antenna Site (W4RNL) Hundreds of Antenna Articles!

Other RF and Antenna Software

• RFGlobalNet Downloads

(links updated 18 Feb 2013)

Learn How Antennas Work!

• Linear Antenna Java Applets

Linear Dipole - set length to 0.5 (half-wavelength dipole) and notice that the impedance is near 73 ohms.  Radiation pattern shown is typical figure-8 pattern. When a half-wave dipole is close to ground, the impedance is lowered to near 50 ohms.  Thus a perfect match to 50 ohm cable.

-set length to 1.27 wavelength.  This is called an Extended Double Zepp antenna and produces the maximum gain possible from a simple center-fed dipole.  Notice that the radiation resistance (impedance) is about 90 ohms.  This antenna can be matched to 50 ohms by using a series inductor. Half of this antenna is 5/8 wave and is a common length for 2m mobile antennas. The 5/8 wave antenna is typically fed against a ground plane (car roof) and is usually matched with a tapped inductor.

-set length of dipole to multiples of 1/4 wave on each side (e.g. 0.5, 1.5, 2.5, etc.).  Notice how these lengths produce an radiation resistance (impedance) close to 100 ohms.  The patterns of these are made up of many lobes (cloverleaf pattern).

How do antennas produce gain?

• dB, dBi, dBd  What is dBi?  What is dBd? What is an isotropic radiator? Part 1 in a series from LB Cebik W4RNL

• Where does the gain come from?  Part 3 in a series from LB Cebik W4RNL

updated 17 Jan 2006

Lincoln Amateur Radio Club Antenna Class

Links to Software and other information

• 4NEC2  Free NEC-2 software with excellent GUI

• Agilent AppCAD  Transmission Lines and more

• MIMP Motorola Impedance Matching Program (select zip file and download)

• NEC User Guides (HTML & PDF)

• Smith Chart resources (articles, software and charts)

• Antenna Modeling Software from Dan Maguire AC6LA (MultiNEC, Moxon generator, TLDetails, etc.)

• KB0YKI's Radio Zone  (online J-Pole Designer, online Yagi Designer, the "Copper Cactus" double J-Pole)

• PCAAD 2.1  Software to help design wire, horn and patch antennas - by Dave Pozar

• RFSim99  

updated 10-21-16

LPCAD - Log Periodic CAD

Now available for Windows 7 and 8!

LPCAD version 3.4 is now available!  LPCAD 3.4 runs fine under Windows 2000, XP, Vista and Windows 7.  Please email me at rgcox2 (at) gmail.com for details.

updated 17 July 2015

NEC Model Library

The following files and links point to NEC/AO/YO models of various Ham antennas that I have simulated and/or tested over the past 30 years as an antenna designer. The NEC files may be used with any of the NEC-2 or NEC-4 programs such as 4NEC2, GNEC or cocoaNEC, however some of them with tapered elements may only be simulated accurately by NEC-4 or other MININEC-based software. These models will indicate in the CM lines if they need to use NEC-4 or 4NEC2. These models have varying degrees of accuracy. Some may be very close to actual performance. Others may only be an estimate. They are for you, as the experimenter, to use and improve.  This list will grow as I check each file before uploading, so check back often. Have fun!

Links:

• W3LPL Yagi Designs  for 40, 20, 15 and 10m

• ARRL library of antenna models

VHF NEC Models:

• 28DX  a 13.4 dBi low backlobe Yagi for 144.2 on a 12' 6" boom

• 215DX a 16.35 dBi low backlobe high-performance Yagi for 144.2 MHz (metric dimensions)

• 216CP  (AO file) a very experimental RHCP 2m beam with 12.3 dBic gain and single point feed

• 216CP (NEC file) - updated 2-4-06 - improved axial ratio & VSWR

• 23DF a 3 element Yagi for 2m Foxhunting (7.7 dBi & 40 dB F/B)

• 25FB a 5 element 4' 4" boom Yagi for 2m Foxhunting  (9.4 dBi & 34 dB F/B)

• 26FB  a 6 element 6' 6" boom Yagi for 2m Foxhunting  (10.4 dBi & 34 dB F/B)

• 27FB  a 7 element 8' 6" boom Yagi for 2m Foxhunting  (11 dBi & 36 dB F/B)

• 6m_3el_yagi  an 8.1 dBi low backlobe Yagi for 50.1 on a 6' boom

• 6m_4el_yagi  a 9.8 dBi Yagi for 50.1 on a 12' 6" boom (use in 4NEC2)

• 6m_moxon a 6.2 dBi "Moxon rectangle" for 50.1 MHz

• LP50-108-16 (NEC file) a Log-Periodic Dipole Array for 50-108 MHz, 8 dBi, 30 dB F/R on 6m, 12' boom

The VHF antennas shown above include the "raw" element lengths.  That is, the element lengths are those used with a wood or plastic (dielectric) boom or supported above or below a metal boom with an large insulator. To convert these raw lengths into actual lengths used when passed through the center of metal booms, you need to add a correction factor, based on whether the element is insulated and passes through the center of a metal boom, or is shorted directly to the metal boom with a clamp.

If the element is insulated when it passes through the metal boom, the correction factor is approximately 1/4 the diameter of the boom.  For example, for a 36" (raw length) insulated element passed through the center of a 1" metal boom, the correction factor is 0.25", so the actual length should be 36.25" when built.

(updated 16 July 2013)

Comments are welcome!

contact Roger: email to 

rgcox2 (at) gmail.com

Roger Cox - Spring Lake, MI