Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD7MW, May 2, 2021.

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  1. EA1DDO

    EA1DDO Ham Member QRZ Page

    Eznec is a business.

    4NEC2 is fully free (no ads, no freeware).

    MMANA is free and open GPL.

    73, Maximo
  2. KD7MW

    KD7MW XML Subscriber QRZ Page

    All of this is very helpful, thanks to you all. I am not going to be designing very complex antennas. I want to avoid tearing my hair out every time I want to do something simple. I'll probably just model simple backyard wire antennas at various heights, do some "what-iffing" re. height and orientation, and fool around with 2m Yagis. If I do anything more complex, it will be to learn about other's designs.

    I get the sense that 4NEC2 does pretty much everything most of us need, but the user interface is often not very intuitive. There are more bugs than there should be. The documentation is not always helpful unless you already know the program. Example: I read that it only works in meters except in some editor that I wasn't using. Yet when I converted a 2 meter Yagi's measurements to meters and entered them, I ended up with a teeny little antenna measured in fractions of inches which couldn't be seen on the screen, and a cryptic bunch of raw NEC errors about every wire being too close to every other wire. It took a while to figure out what had happened, and I had to redo everything. This was probably a typical newbie mistake, but it was very frustrating.

    I made my original post while exploring various methods to comply with the U.S. RF Safety rules. EZNEC displays near field tables, with a long legal disclaimer that the program may not be used to determine the safety of a human being, even though the FCC accepts it for regulatory compliance purposes. This is probably more about the author protecting himself against lawsuits than it is about the program's accuracy relative to any other program, but it's not very encouraging! EZNEC is very well documented. The docs includes many explanation of "how to" and "why," rather than the typical engineer's list of functions without context. It has attained the rank of "the standard" in the U.S. Lots of American examples and ARRL articles refer to EZNEC. The trial version is pretty much useless beyond a simple dipole or vertical. If you're going to use EZNEC, you're going to pay $100, maybe $150, plus future upgrades. It doesn't allow variables, unlike the other two.

    4NEC2 has wonderful graphical displays, including a nice 2D color display of the three near field planes. You can easily set the colors to display MPE limits. But I found that sometimes after clicking on the graphic, the program sometimes shows the wrong XYZ coordinates when I move the cursor, and even after I move it out of the display area. I've read of other annoying bugs like this. The program is no longer being developed, so the bugs won't be fixed. One very nice thing is that it will read EZNEC files and convert them to .NEC files. So even if a person doesn't use EZNEC, all of the many .EZ models posted by other hams may be imported into 4NEC2.

    MMANA-GAL basic (free) version does not do near fields. nor does it have an undo function. The paid "personal Pro" version, 139 Euros, has both those things. It seems to be the easiest to use of the three programs overall. It only works in meters, but one can enter a model in feet or inches by specifying n.nnn*f or *i, and the the program will do the conversion. There appear to be limitations on ground models, and the program doesn't handle the effect of wire insulation. I don't know if it can import or export any other program's files. There is a vast library of antenna designs created with it. It seems to be "the standard" in Europe.

    Correct me if I'm wrong on any of this. It seems like the more I learn, the more difficult the choice is. On one hand, this, on the other hand, that... :)

    Last edited: May 3, 2021
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

  4. KX4OM

    KX4OM Ham Member QRZ Page

    That is me; I am guilty of that. However, I am studying the "Antenna Physics" book by Bob Zavrel, and it is a revelation. I'm starting Chapter 4 tonight. I'm looking forward to Chapter 6, "Dielectric Effects on Radio Waves" because I've been following a very deep (and contentious) thread on verticals, modeling, radiation resistance and ground losses on the eHam forum. I'll be starting to do some work on 4nec2 shortly.

    The only modeling I've done like this is developing the physical model of radiation sources (gamma radiation in piping) and targets (electric motor-operated valves) for safety-related systems in nuclear power plants, working with system piping and instrumentation drawings (P&IDs) and 3-D physical layout drawings back in the early 1980s. String of gamma point sources simulating line sources, sort of like Method of Moments, running in Fortran. Punch card decks in and line printer results out :)

    Ted, KX4OM
  5. K6CLS

    K6CLS Ham Member QRZ Page

    That's a really great book!! I've read it several times, each time I get more and more out of it.


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