On Tue, 23 Sep 2008 19:09:10 -0700 (PDT), Art Unwin
wrote:

Incidentally, MMANA-GAL Yahoo Group:
http://groups.yahoo.com/group/MM-HAMSOFT/

Does this have unlimited segments and variableswith it's optimizer?

I couldn't find any documentation as to the program limits. As I
understand it, MMANA-GAL has a stripped down NEC2 engine. 4NEC2 and
EZNEC use the full NEC2 engine from Lawrence Livermore Labs. I'm not
sure what you're building but allow me to offer a clue. I recently
threw together a model of a truly ugly tower with about 8000 segments
including about 2000 pattern lines for various grids and reflectors.
After about 14 hours running, my PIII/933MHz finally spewed out a
result (that told me that I goofed and had to make corrections). I
dragged home a P4/2.8GHz with hyperthreading, which took about 8 hours
to run. This was getting ridiculous, so I dragged the program and
model to a customers office, and ran it overnight on his P4 2.8GHz
dual core, 4GB RAM, 1333MHz FSB, SATA2 drive, etc. It doesn't get
much better. It ran in 3 hours.

The optimizer isn't much better. It will automagically tweak
dimensions to meet a pre-defined set of criteria. If you set the
final criteria too close to perfection, you may get an answer after
the next ice age.

Anyway, I suggest you use a machine with lots of horsepower and start
with EZNEC, 4NEC2, NEC-WIN, MMANA-GAL, or other modeling program using
some of the sample files included with each program. Once you have
figured out how to manipulate and modify those, you can step up to
more complexicated models (such has the giant mess I stupidly created
by throwing every piece of metal on the tower into the model).

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Thanks for the effort Jeff, but for some reason it doesn't seem to be
compatible. It won't open as an NEC file and I also tried giving it
just an NC tag. The closest I can get is importing it as a card deck,
but it says it has errors, and when I look at the code, it looks
totally different from other formulas that do work in the app.

Art, it does have variables... I don't know if the segments are
unlimited. It seems to work great with the included files. Normally
I'm pretty good at this stuff. I can do my own html and some other
code stuff, but I'm just having difficulty getting a grasp on this for
some reason. I did find a tutorial for NEC and read the whole thing,
but it didn't help much. I guess I'm not great with the scientific
stuff.

Dave

On Tue, 23 Sep 2008 22:50:04 -0700 (PDT), wrote:

Thanks for the effort Jeff, but for some reason it doesn't seem to be
compatible.

Can you read the .NEC file as a text file with an editor? I might
have tossed in a few extra carriage returns, word wrapped it, or
something equally stupid. Maybe some extra characters at the
beginning or end?

It won't open as an NEC file and I also tried giving it
just an NC tag. The closest I can get is importing it as a card deck,
but it says it has errors, and when I look at the code, it looks
totally different from other formulas that do work in the app.

An NEC file is a card deck. I have a Mac Cube with OS/X sitting in
the office. When I have time (which means after Sunday), I'll see if
I can feed it to cocoaNEC and see what breaks.

I'm pretty good at this stuff. I can do my own html and some other
code stuff, but I'm just having difficulty getting a grasp on this for
some reason. I did find a tutorial for NEC and read the whole thing,
but it didn't help much. I guess I'm not great with the scientific
stuff.

NEC user guide and manuals:
http://www.nec2.org

EZNEC 5 manual:
http://www.eznec.com/ez50manual.html

Basic Antenna Modeling by L.B. Cebik:
http://www.nittany-scientific.com/book/index_beg.htm

Advanced Antenna Modeling by L.B. Cebik:
http://www.nittany-scientific.com/book/index_inter.htm

Antennex Guest Room:
http://www.antennex.com/guests.html
Get a login and password. Lots of goodies inside including plenty of
tech articles, CD's full of past issues, etc.

ARRL Antenna Modeling page with plenty of documents and links at the
bottom of the page:
http://www2.arrl.org/tis/info/HTML/antenna-modeling/index.html

NEC misc programs, docs, examples, whatever. Somewhat old:
http://www.si-list.net/swindex.html

There's probably more but that should keep you occupied for a while.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tue, 23 Sep 2008 22:50:04 -0700 (PDT), wrote:

Thanks for the effort Jeff, but for some reason it doesn't seem to be
compatible.

Ok, if all else fails, we use brute force.

-------- cut here ------------

CM J-antenna 144MHz
CE

sy H=7.12 ' Height above ground

SY l1=0.47, la=H+l1
SY l2=1.483, lb=H+l2

GW 1 20 0.0 0.0 la 0.0 0.0 lb .003
GW 2 10 0.0 0.0 la 0.0 0.0 H .003

SY d=0.0354, dd=H-d
GW 3 1 0.0 0.0 H 0.0 0.0 dd .003
GW 4 1 0.0 0.0 dd 0.0 .01 dd .003
GW 5 1 0.0 .01 dd 0.0 .01 H .003
GW 6 10 0.0 .01 H 0.0 .01 la .003
GW 7 1 0.0 0.0 H 0.0 .01 H .003
GE 1

EK
LD 5 0 0 0 25000000
GN 2 0 0 0 13 0.005 0.0 0.0
EX 0 7 1 0 1.0 0.0
FR 0 1 0 0 145 1
EN

-------- cut here ------------

What can go wrong, go wrong, go wrong, go wrong....


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:

I couldn't find any documentation as to the program limits. As I
understand it, MMANA-GAL has a stripped down NEC2 engine. 4NEC2 and
EZNEC use the full NEC2 engine from Lawrence Livermore Labs. I'm not
sure what you're building but allow me to offer a clue. I recently
threw together a model of a truly ugly tower with about 8000 segments
including about 2000 pattern lines for various grids and reflectors.
After about 14 hours running, my PIII/933MHz finally spewed out a
result (that told me that I goofed and had to make corrections). I
dragged home a P4/2.8GHz with hyperthreading, which took about 8 hours
to run. This was getting ridiculous, so I dragged the program and
model to a customers office, and ran it overnight on his P4 2.8GHz
dual core, 4GB RAM, 1333MHz FSB, SATA2 drive, etc. It doesn't get
much better. It ran in 3 hours.


If your optimization is just changing a small part of the overall
structure (e.g. the position of an antenna on the tower), then you
should be looking at the Write Greens Function and Read Greens Function
cards.
http://www.nec2.org/part_3/ngf.html

This is how they do things like analyze antenna placement on a ship or ISS.

wrote:
Thanks for the effort Jeff, but for some reason it doesn't seem to be
compatible. It won't open as an NEC file and I also tried giving it
just an NC tag. The closest I can get is importing it as a card deck,
but it says it has errors, and when I look at the code, it looks
totally different from other formulas that do work in the app.

Art, it does have variables... I don't know if the segments are
unlimited. It seems to work great with the included files. Normally
I'm pretty good at this stuff. I can do my own html and some other
code stuff, but I'm just having difficulty getting a grasp on this for
some reason. I did find a tutorial for NEC and read the whole thing,
but it didn't help much. I guess I'm not great with the scientific
stuff.


NEC takes some getting used to, and, the tutorials that come with it are
aimed at computational electromagnetics folks, who already understand
how NEC works under the hood, and are really looking at "how do I put my
problem into a form for THIS particular code".

There's some pretty common "tricks of the trade" used with NEC, like
using a network to create a current source (4nec2 does this for you
automatically).

Mostly, though, it's just slogging through it the first few months until
you get your mind wrapped around the conceptual model.

Start with something fairly simple (but non trivial).. like a multiband
dipole or a 3 element Yagi with just wires (i.e. don't start out trying
to model the U-bolts and stuff).

A dipole is nice to fool with, because you can put a wire in under it to
represent a tower, for instance, and see what effect it has on the
pattern. Likewise, you can do something like model your rain gutters or
the feedline as a single wire, and see how much current is induced in them.

It just keeps saying each line in that formula has a syntax error.
Hmm.

Well, I'll start reading all of that stuff... Maybe it will sink in.

On Wed, 24 Sep 2008 10:39:47 -0700, Jim Lux
wrote:

If your optimization is just changing a small part of the overall
structure (e.g. the position of an antenna on the tower), then you
should be looking at the Write Greens Function and Read Greens Function
cards.
http://www.nec2.org/part_3/ngf.html

This is how they do things like analyze antenna placement on a ship or ISS.

Thanks. I haven't done much with the optimizer beyond tinkering to
see how it works. I've never tried the NGF feature, but it certainly
looks interesting. Looking at the above page, I'm instantly lost.
However, I'll be taking yet another medical vacation shortly, so I'll
have plenty of time to RTFM.

Incidentally, the tower in question is at a friends radio site. It's
loaded with a mixture of commercial, FM translator, and ham systems.
There was almost no planning in the tower antenna arrangement. The 2
ton gorilla in the mix are 3ea 250 watt 900MHz paging xmitters, that
are causing problems with the other users. I can't touch their
antennas because they pay the bulk of the bills. There are also some
nulls that need to be moved to placate some of the customers. I'm
trying to first model, and later optimize the location of the other
antennas. So far, simple solutions like vertical isolation and
positioning antennas on opposite sides of the tower from the paging
antennas look promising. Sorry, no photos as the owner wants me to
keep the location secret.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

On Wed, 24 Sep 2008 11:44:26 -0700 (PDT), wrote:

It just keeps saying each line in that formula has a syntax error.
Hmm.

Yep. I just got the same error (after wasting 30 mins doing updates).

"Syntax Error in external declaration: identifier CM"

CocoaNEC can't even parts a CM (comment) declaration. Something is
wrong. I found the examples for CocoaNEC at:
http://homepage.mac.com/chen/w7ay/Manuals/cocoaNEC/Manual/examples.html
which work as expected. I figured out that it wants to import a .NEC
files as a "spreadsheet". However, when I try that with the Jpole
file, I get "Cannot open xxxxx. File may have moved or been deleted".
After that, CocoaNEC "quits unexpectedly" and wants to know if it
should stay dead or restart. Lovely mess. I'll work on it some more
later tonite or this weekend. I may even RTFM.

Incidentally, my Mac G4 Cube only has 384MB of RAM, which may be the
problem.
http://en.wikipedia.org/wiki/Mac_Cube

Well, I'll start reading all of that stuff... Maybe it will sink in.

Not if you can't run a simple model with CocoaNEC. Have you
considered switching to the dark side and getting a PC? I haven't
tried running 4NEC2 or EZNEC under Bootcamp or one of the Windoze
emulators on OS/X but that might be worth a try.



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

On Wed, 24 Sep 2008 19:34:29 -0700, Jeff Liebermann
wrote:

It just keeps saying each line in that formula has a syntax error.
Hmm.

I broke down and read the documentation.
File - Import Card Deck
Load the Jpole.NEC file. It shows up correctly in the "card view" but
fails to appear in the "element inspector" and "spreadsheet view".

When I try to run it anyway, it complains with:
"NEC-2 error. Possible wire element that touches z=0".
No clue which card (line) it hates.

I'm going to give up in disgust for tonite.
Y're on your own for now.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS