Lawrence Livermore Labs NEC2 manuals:

Part1: http://www.wuala.com/300ohm/Documents/nec2manual1.pdf

Part2: http://www.wuala.com/300ohm/Documents/nec2manual2.pdf

Part3: http://www.wuala.com/300ohm/Documents/nec2manual3.pdf

I think theyre still on Arie Voors site too.

thanks a lot!

hey, I was hoping to find it in the section V, modeling, of part 1, but even reading down the middle you can get lost in the electrical integrals !

makes you appreciate whats behind that program though!

Sure does, heh. Imagine trying to do the calculations by hand, heh.

not sure im using the optimizer correctly, and I wonder if anyone here has tips on using it...


one item ive noticed is you get it (over a long time) to give almost any gain (quite high relative to the start point) and force the SWR to a pretty decent minimum, but when you run the AGT on the new geometry, most of the time you lose almost evrything you think you gained, so im not sure the point of it if it wastes a lot of time to end up with misleading results...is there a specific strategy to follow to get the most out of the various optimizer modes?

I find the help menu on this topic is very confusing, and limited

Yes, on that same website where you downloaded the program, there are pdf files to download and read (NEC beginners guide (nec_partX.pdf) in English, German and French. Read that first. Then there is a _Get_Started.txt file in your 4nec2 program folder with a step by step tutorial.

Can I find this file anywhere else? Or does anyone have it and can send it to me? It appears they have removed it or blocked it for some reason?

Here ya go.

http://www.wuala.com/300ohm/Documents/_GetStarted.txt

I optimized using the evolver, on 470 to 704, step=6, total gain, theta=90, Phi=0, resolution=0

the nec file has the following cards:

FR 0 39 0 0 470 6
RP 0 1 73 1510 90 0 1 5


then I did a manual far field pattern run,

on 473 mhz:

-for HOR, theta=80, gain= 12.8
-for HOR, theta=90, gain=12.6
-for FULL, theta=80 (max gain), gain=11.7

on 585 mhz:

-for HOR, theta=80, gain= 12.8
-for HOR, theta=90, gain=12.6
-for FULL, theta=90 (max gain), gain=13.1


now doing a freq sweep (using "original" file), i get on the gain graph,

-on 473 mhz, theta=90, gain= 12.6
-on 585 mhz, theta=90, gain= 14.2

1. im trying to understand why in the manual far field runs, the FULL results dont match the HOR results

2. and why the frequency sweep results dont match the manual far field run results

:confused:


thanks

on 585 mhz:

-for HOR, theta=80, gain= 12.8
-for HOR, theta=90, gain=12.6
-for FULL, theta=90 (max gain), gain=13.1
That should make sense if you do a 3D pattern. The max gain isnt dead ahead.

That should make sense if you do a 3D pattern. The max gain isnt dead ahead.


so i guess the question is what is FULL / TOTAL, is that because it includes a Vertical component of gain? and if so we should always be interested in the TOTAL gain (as opposed to HOR.)?

Yes, but it depends on the type of graph you want to output. See Help > Calculate data > Generate output data.

when I run a generate, or optimize, im getting 4nec2x Run-time error '6' Overflow with "!", then I have to kick myself out of the file,

also getting ! NEC: geometry data error -- segment 1 lies in plane of symmetry


any ideas? thanks

Post the file so we can see.

Ok i think its because I used the GX card after a certain part of the structure's GW cards, and it flipped the one part into the plane of the other, so I moved the GX card to another appropriate place and it seems to work now!

as for the run-time error, it seems like the optimizer didnt like having too many variables include all at once!

EDIT: it turns out it didnt like one variable in particular, which marked the centerline (z-axis), CL=0, (about which I used the symmetry card GX, I made CL a very small value >0 and the optimizer accepts it noW!?:eek:

In Settings > Memory Usage > Max-nr of SYmbols, you may have to increase the default number. (probably would be a good idea to have at least 1GB of computer memory when increasing the defaults)

I get the warning about wire volumes intersecting, the wires seem to not actually touch each other though, is this normal, or does it matter?

Thats a correct warning/error in all the cases Ive seen. The 3D model display doesnt correctly scale the viewed wires. Look closely at the wire size you used for the adjacent wires and I think youll find the error. Remember the input is the Radius of the wire. Check your decimal point places.

not sure I understand the difference between "volumes" intersecting, as opposed to wire intersecting....

for the volumes it appears the wires dont touch one another, not in the geo edit view, nor even after doing a geometrical calc

???

not sure I understand the difference between "volumes" intersecting, as opposed to wire intersecting....
I think its basically the same thing, with an pure intersection meaning 100 % of each of the volumes intersecting and with volumes intersecting, it could be less than 100 %.

An example would be a 1" boom (.5" radius) and a 3/8" element (.1875" radius) that are 9/16" away from each other. Remember, the coordinates in NEC2 are center of wire, so a piece of the 3/8" element would be digging into the 1" boom.

thanks, makes sense, I kept forgetting that the geo edit isnt scaling the diameters!

still learning....:eek:


also, I get the "sharp angle" warnings for a bunch (4-6) wires meeting at an acutish angle....does this matter, because if I resegment it throws the segmentation criteria off....do I need to break the element into several wires, and segment each wire piece differently (eg 1 segment on 1 piece of wire at the acute angle end)?

thanks

also, I get the "sharp angle" warnings for a bunch (4-6) wires meeting at an acutish angle....does this matter, because if I resegment it throws the segmentation criteria off....do I need to break the element into several wires, and segment each wire piece differently (eg 1 segment on 1 piece of wire at the acute angle end)?



how is it possible to determine if these warnings, if left unaddressed, are affecting the results, I would assume the AGT will go WAY off, is that so

I also have seen the message, when optimizing, "structure out of range"...not sure if thats related