Tag Archives: NEC

Getting NEC5 to work with EZNEC

First off, yes the instructions are in the EZNEC manual (page 60). I eventually found them by searching the manual. And a further yes, they are a bit less than intuitive.

With you licensed copy of NEC 5.0 X.13 downloaded, and EZNEC installed on your system:

  1. Unpack the NEC 5.0 X.13 folder, putting a copy of the whole folder in the \EZNEC 7.0\Docs\ folder EZNEC previously created.
  2. Start EZNEC, selecting Options>Calculating Engines>NEC 5
  3. When prompted navigate to the .exe in the NEC 5.0 X.13 folder and select the non-32bit .exe (unless you know you need the 32 bit one for your system, then us that one) (The manual file names are for an older X.11 version of NEC 5.0)
  4. The system should ask you to associate model file names with the engine, to which you say yes.
  5. Save the new configuration as Options>Default
  6. You can later confirm through EZNEC Utilities Menu that all is good.

If you are running the free trial version AutoEZ and have downloaded the NEC 5.0 X.13 test models AutoEZ provides, you will find they won’t run as they have too many elements for the trial version. The NEC 5.0 X.13 Antenna Model test files work under the licensed version of AutoEZ though.

Note that NEC 5.0 updated how Objects are Placed (read page 97) and there are some tradeoffs  (see table on page 180).  The appears to mean that if you want to run your models both with the built-in EZNEC NEC-2 (called EZCalcD) and the External NEC 5.0 engines, you likely will need to make two models to properly place the objects that make up your antenna model.



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Buying a NEC-5 License for Antenna Modeling – Lawrence Livermore National Laboratory

Buying a NEC-5 License for Antenna Modeling – Lawrence Livermore National Laboratory, you get to work with Mary Holden-Sanchez, who is super nice as well as efficient.

As of mid-May 2022 the process is you should fill out the three forms and get them to Mary by email. Several are pdfs that you can fill in online prior to saving them and sending them. On the long license form fill in everything you can BEFORE you let Adobe do its eSignature part, as there are parts to be done after the signature page.

I withheld some of my credit card details rather than sending them via email, and I called in the missing parts.

Lawrence Livermore National Laboratory can also do payment via DocuSign, an interim solution providing much better security for your credit card details. To request the DocuSign process, email Mary.

They are in the process of implementing a secure online payment system.

The link for NEC-5 is https://ipo.llnl.gov/technologies/it-and-communications/nec-v50-numerical-electromagnetic-code

The May 2022 contact, and Mary’s information is:

Mary Holden-Sanchez, IP Specialist
Innovation & Partnerships Office (IPO)
Lawrence Livermore National Laboratory

My experience is that the system has an unusual number of moving parts, that adding the financial security will be a boon for the payees & LLNL, that some of the people are working from home, and that at this time the payment part is done by finance separately from licensing.

When everything goes through, you get an email invite to your portal where for about the 3rd or 4th time you get enter your contact information before you can download the files.

As it was, I missed the daily cutoff for payment processing and it took a day to get my license.

On the plus side, they have a really great product to license and I got to speak with good people!  I’ll touch how to add NEC 5.0 X.13 to your installation of EZNEC in another post.



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More on Antenna Modeling

The previous post on EZNEC being offered gratis to the Amateur Radio community had some comments, and I received a few emails. (Link https://k9zw.wordpress.com/2022/05/14/eznec-antenna-modeling-for-all-of-us/ )

Much of what had been in computer antenna modeling has changed over time.

I gathered as many links as I could find for this post.  If you know of additional programs or links, please put them in a comment, and periodically I will edit them into the main post.

(NOTE:  Focus is on general HF Amateur Radio level usage programs)

Antenna Modeling Links – mid-May 2022:

Active Programs Found

Linux Active Programs Found

Links that work, but the programs are not fresh (may be DOS or WinXP):

Replaced by newer offerings

Defunct Links

  • NEC-Win-Plus – defunct was Nittany Scientific, who is out of business
  • NEC4WIN – defunct – was Orion Systems
  • SuperNEC – defunct

About NEC (the engine at the center of these programs)

NEC Alternatives/Derivatives

Other Useful Links:

ARRL Links



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EZNEC Antenna Modeling for All of Us

I missed this while it was happening. I was looking to update my old software to model my new antenna configurations and found out about the change.

As Roy W7EL decided to retire, he made public his EZNEC antenna modeling software (compiled form only).


There is also some neat stuff on NEC-5 end, where there is a collaborative update to the latest version (NEC5 X11) thanks to some great ham inputs! https://eznec.com/NEC-5.htm

The AC6LA add-on AutoEZ is something I plan to check out. https://eznec.com/AutoEZ.htm and https://ac6la.com/

AutoEZ is interesting as it an an Add-On to EZNEC which in also in essence an Add-On to NEC.  AutoEZ appears Excel-based, EZNEC is Visual Basic 6 (obsolete version) with some Fortran modules,  and the core NEC compiled Fortran (Intel Visual Fortran with the mkl math libraries).

Below the “–” line I will include some background from either Roy W7EL (website archived copy or QRZ.com) or a QSO Today Podcast interview he did with Eric 4Z1UG.

Well worth checking out all of these programs.

Also a series of dedicated books by ON5AU that should be considered if you are going to put EZNEC to work:



GL and 73


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