Antenna modeling programs, some questions ...

[KC2ZPK]

OK, I have used the EZ-NEC demo, and for a demo it is ok, but I think I am going to need more then what it will do to model some beams I would like to try out. What other modeling programs are there, that won't break the bank? And do any of them use some sort of graphical interface, such as Autocad, EZCad, TurboCad, to draw the elements, instead of having to input points manually?

Thanks
73

 

[Marconi]

OK, I have used the EZ-NEC demo, and for a demo it is ok, but I think I am going to need more then what it will do to model some beams I would like to try out. What other modeling programs are there, that won't break the bank? And do any of them use some sort of graphical interface, such as Autocad, EZCad, TurboCad, to draw the elements, instead of having to input points manually?

Thanks
73

I think 4nec2 is free. I also think it lets you model your antenna on a scaled graphical platen. I could be wrong though and I'm not sure how that handles three dimensions. I think this platen then converts the image to the x,y,z data points and then runs the NEC engine.

I guess you are having segment problems with your beam designs, right?

 

[KC2ZPK]

yes. too many and too long

Sent from my Incredible.

 

[Marconi]

yes. too many and too long

Sent from my Incredible.

Since you are limited to 20 segments with the Demo version, you have to use fewer segments and that limitation results in each segment being longer than it should be in many cases. Sometimes the segment warning will appear as a caution, but the model will still run. Model accuracy may be ill-affected however. A dipole is about the limit for the Demo version.

I use the first upgrade version of EZ5 and I'm allowed 500 segments. Sometimes that reaches the limit even with simple CB type vertical monopoles. To really do beams with a lot of wires on many elements you probably need a segment limit above 1000, and I think 4nec2 is over 10,000. In addition 4nec2 has an optimizer function that could come in real handy trying to model beams.

Do a search for 4nec2 on YouTube, there is a really good 5 part video on its use. Sorry I don't think I have the link, but if I find it I will post it up for you. Check here:

http://www.youtube.com/watch?v=bEIWUid_wio

Good luck and keep me posted.

 

[KC2ZPK]

Yes, 20 is too few. I down loaded MMANA, I think I also downloaded 4NEC2 as well, I am sure I will try both. I am trying to home brew a hexbeam type of beam. There are several versions of home built hexes, and I figured I would give it a try as well. There are also several models of hexes to try out in the simulation programs. I'll keep you posted.

 

[ghz24]

4nec2

I use 4nec2 it is best free modeling program I've found. I've been playing with it for about a year and a half now.
It should come with an addictive program warning :wub:
I recently remembered all the strange looking CB antennas I remember seeing pop up during the 70s craze and thought I'd model some of them just to see how they work and what happens if....
I have a few (CB) models already ( lots of TV).
I wasn't familiar with the hexbeam but now I have to model one.
I can post a model in a few days if anyone is interested.

 

[Marconi]

I use 4nec2 it is best free modeling program I've found. I've been playing with it for about a year and a half now.
It should come with an addictive program warning :wub:
I recently remembered all the strange looking CB antennas I remember seeing pop up during the 70s craze and thought I'd model some of them just to see how they work and what happens if....
I have a few (CB) models already ( lots of TV).
I wasn't familiar with the hexbeam but now I have to model one.
I can post a model in a few days if anyone is interested.

I would be interested to see what you produce 24. If you can send me the file, it might get me interested in trying to work 4nec2 as well. It really looks cool, but I just haven't been stimulated enough yet to give it a shot.

The main screen is pretty bussy, and I don't think I've run across a manual for 4nec2 yet. Is there one that comes with the download? If so, can you point me in that direction too.

Thanks,

 

[BOOTY MONSTER]

i wouldn't put too much faith in them . not matter how much information is put in they seem to never show results that apply to everyone . and we're still stuck with not knowing what a antenna will do at a particular location till its put up . then , if you move it up/down or left/right a few feet you could get noticeably different results .....

 

[GnG8d]

i wouldn't put too much faith in them . not matter how much information is put in they seem to never show results that apply to everyone . and we're still stuck with not knowing what a antenna will do at a particular location till its put up . then , if you move it up/down or left/right a few feet you could get noticeably different results .....

That's why you are better modeling the antenna in free space.


Sent from my iPhone using Tapatalk

 

[BOOTY MONSTER]

does anyone actually use a antenna in free space ..... other than astronauts ?

 

[Marconi]

does anyone actually use a antenna in free space ..... other than astronauts ?

You see 359, you're right, but BM has the idea that free space models are done in outer space...somewhere between the Earth and the Moon maybe, at best a figment of his imagination.

Even though I have attempted to describe the idea of a free space model to BM, he refuses to consider what it really might mean: the absence of the very conditions (losses) that he has suggested to us above...that potentially makes a difference in every real world installation.

 

[BOOTY MONSTER]

can you post a pic of the "free space" at your 20 that you use for testing OGP ?

 

[Marconi]

can you post a pic of the "free space" at your 20 that you use for testing OGP ?

Sure I can, but only those that have faith and understanding would know what it is their looking at, and unfortunately that leaves you out.{Cry_river}

 

[BOOTY MONSTER]

LOL
i guess if the software simulations reflected every ones results with the antennas modeled that i'd have some faith in them .
but since different folks have different results with the same antenna in different locations .... well ... you get the idea .

 

[ghz24]

Wow I sparked a debate.

B Monster: no program or simulation is going to take all the infinite little variables that make up your location and trying is an exercise in futility.

But that's the point if I want to directly compare antennas I get rid of extra variables and go to free space.

If you want hints as to the TOA at some height over some approximated/averaged ground then ya that's about the accuracy you can expect (ballpark approximations) but even those can be interesting and reveal trends.

Marconi:

This is a tribeam (Antenna Specialists "Super Scanner") I built to try and see how they could be steered electrically. (no rotor)
I tried to find a model that was not to complex but still have some variables to play with in the optimizer ( or by hand).


Just copy and paste this into a text file and save it as "whatever.nec" in the models subfolder. Then use 4nec2 to open it.

CM 11 meter cb by ghz24
CM tri-beam testbed steering test
CE
SY sep=130.7936
SY z=109.1327
GW	1	9	sin(30)*sep	sin(60)*sep	0	sin(30)*sep	sin(60)*sep	2z	0.05260011
GW	11	9	sin(30)*sep	-sin(60)*sep	0	sin(30)*sep	-sin(60)*sep	2z	0.05260011
GW	3	9	-sep	0	0	-sep	0	2z	0.05260011
GS	0	0	0.0254
GE	0
GN	-1
EK
EX	0	1	5	0	1	0
EX	0	11	5	0	1	0
'EX	0	3	5	0	1	0
FR	0	0	0	0	27.18	0
EN

The ' character is comment/ignore
I think there is a user manual available from the help menu if you have open office or MS office (I think it's in .doc format).
But I'd advise just play and poke first and see how much reference you need.

The geometry editor can remove all variables from models and leave only numbers just open in geo editor and save as new name (it will warn you about removing variables). I use all 4 editors for different things. Try the 2nd one down first it labels the fields and highlights the wire in geometry view window (F-3).
I'll have a hexbeam model in a couple days.