Help with slim jim nec model
 

I'm trying to create a model for a slim-jim type of jpole in NEC, but
I'm having a hard time figuring out how the coordinates should go in.
Can anybody help me with some hints? If I can get where each side
basically goes in X Y & Z and the feed, I can probably get the rest.
Or maybe there's a file online somewhere? I wouldn't mind figuring out
how to do a UHF/VHF log either. Thanks,

Help with slim jim nec model
 

On Fri, 19 Sep 2008 01:13:20 -0700 (PDT), wrote:

I'm trying to create a model for a slim-jim type of jpole in NEC, but
I'm having a hard time figuring out how the coordinates should go in.
Can anybody help me with some hints? If I can get where each side
basically goes in X Y & Z and the feed, I can probably get the rest.
Or maybe there's a file online somewhere? I wouldn't mind figuring out
how to do a UHF/VHF log either. Thanks,

Draw either on a piece of graph paper. You will have your coordinates
that way when you mark up the grid.

73's
Richard Clark, KB7QHC

Help with slim jim nec model
 

On Fri, 19 Sep 2008 01:13:20 -0700 (PDT), wrote:

I'm trying to create a model for a slim-jim type of jpole in NEC, but
I'm having a hard time figuring out how the coordinates should go in.
Can anybody help me with some hints? If I can get where each side
basically goes in X Y & Z and the feed, I can probably get the rest.
Or maybe there's a file online somewhere? I wouldn't mind figuring out
how to do a UHF/VHF log either. Thanks,

Go unto:
http://mmhamsoft.amateur-radio.ca/mmana/index.htm
and download MMABA-GAL modeling software. It's free. Included in the
samples is a 145MHz J-Pole antenna as:
\ANT\VHF\J-ant144.mma

For NEC2 output, see utility at:
http://www.qsl.net/ua3avr/
which is the same engine used for 4NEC2 (by the same author).

More antenna models at:
http://dl2kq.de/mmana/4-3.htm

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

Help with slim jim nec model
 

Jeff Liebermann wrote:
[stuff]

What amazed me, after looking them both over, eznec/mmana-gal, the
similarities are greater than their differences ... could the
instructions/examples from eznec be useful?

Just a thought,
regards,
JS

Help with slim jim nec model
 

On Sat, 20 Sep 2008 19:49:21 -0700, John Smith
wrote:

Jeff Liebermann wrote:
[stuff]

What amazed me, after looking them both over, eznec/mmana-gal, the
similarities are greater than their differences ... could the
instructions/examples from eznec be useful?

Yep. 4NEC2 will open .EZ files from EZNEC directly. I'm not very
familiar with MMANA-GAL but it appears that Ari's utility will both
import and export .NEC files.

Any tutorial from any vendor is useful. There's no reason to just use
one modeling program. If you had a workshop, would you use one tool
for every job? Probably not. If you sign in to the free Antennex
"guest room", there's a rather long and detailed NEC2 manual, along
with lots of tutorials and articles from back issues.

However, despite the wealth of tutorials and articles, I find it best
to learn by destroying. I hate to recommend my method because it's
not for everyone, but I like to start with a similar model, and
butcher it so I know how it works and what it does. If I can't figure
out how to do something, I search and read the docs. Not the best
method, but works for me.

I use mostly 4NEC2 because I'm familiar with it and because it
includes a surface, dish, cylinder, etc generator. I sometimes use
the free version of EZNEC, because it's somewhat easier to use. I
also use NEC-Win Synth to build tower and geometric structures:
http://www.nittany-scientific.com/nws/index.htm

There are lots of antennas available at various sites to plagerize.
For example:
http://www.nittany-scientific.com/examples.htm
http://www.cebik.com
http://www.antennex.com

Drivel:
Various commercial digital TV antennas:
http://www.hdtvprimer.com/ANTENNAS/comparing.html
with Eznec NEC2 files at:
http://hometown.aol.com/kq6qv/SIMS/
I'm amazed at how well some of these antennas work over the very wide
TV VHF/UHF range. In the past, I've assumed that much of the metal
work on the typical TV antenna were decorations and that the antenna
was at best a marginal proposition. Apparently not, as most of the
commercial antennas seem to be rather well designed.

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

Help with slim jim nec model
 

Jeff Liebermann wrote:
[real stuff]

Uh, Jeff ...

Eznec vs. Mmana-Gal ... be careful--play dumb ... :-)

Regards,
JS

Help with slim jim nec model
 

On Sat, 20 Sep 2008 21:15:01 -0700, John Smith
wrote:

Jeff Liebermann wrote:
[real stuff]

Uh, Jeff ...
Eznec vs. Mmana-Gal ... be careful--play dumb ... :-)

You left out about a dozen other packages including 4NEC2. I've never
played dumb and don't plan to start now. What am I missing? Some
kind of religious issues in modeling software? A battle to the death
between the fanatics? Conflicting results?

Well, actually.... I did play dumb once. I came face to face with a
mountain lion on a hiking trail. Trying to act non-threatening does
not come naturally to me.

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

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

Help with slim jim nec model
 

Thanks for the help... I'm actually using cocoaNEC for OSX, so
unfortunately I can't use those files. Otherwise that would probably
be a big help. I know if I could just see one example of each, I could
adjust the rest myself.

Help with slim jim nec model
 

On Sep 21, 12:11*am, Jeff Liebermann wrote:
On Sat, 20 Sep 2008 21:15:01 -0700, John Smith

wrote:
Jeff Liebermann wrote:
[real stuff]

Uh, Jeff ...
Eznec vs. Mmana-Gal ... be careful--play dumb ... :-)

You left out about a dozen other packages including 4NEC2. *I've never
played dumb and don't plan to start now. *What am I missing? *Some
kind of religious issues in modeling software? *A battle to the death
between the fanatics? *Conflicting results?

Well, actually.... I did play dumb once. *I came face to face with a
mountain lion on a hiking trail. *Trying to act non-threatening does
not come naturally to me.




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


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








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

Help with slim jim nec model
 

On Tue, 23 Sep 2008 17:40:28 -0700 (PDT), wrote:

Thanks for the help... I'm actually using cocoaNEC for OSX, so
unfortunately I can't use those files. Otherwise that would probably
be a big help. I know if I could just see one example of each, I could
adjust the rest myself.

No problem. We'll do it differently and easier. Here's the NEC2 file
for a 145MHz JPole for stolen from the 4NEC2 samples.
http://802.11junk.com/jeffl/crud/J-ant.nec

I just discovered that the conversion program from .MMA to .NEC will
generate a perfectly usable .OUT file, but not a .NEC input file. I'm
probably doing something wrong, but I don't have time to debug it
right now.

Note to self: Make an index of .NEC files. It's becoming difficult
to find specific antennas.


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

Help with slim jim nec model
 

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

Help with slim jim nec model
 

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

Help with slim jim nec model
 

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

Help with slim jim nec model
 

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

Help with slim jim nec model
 

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.

Help with slim jim nec model
 

Help with slim jim nec model
 

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.

Help with slim jim nec model
 

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

Help with slim jim nec model
 

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

Help with slim jim nec model
 

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

Help with slim jim nec model
 

On Sep 24, 8:13*pm, Jeff Liebermann wrote:
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.


Thanks for all the effort... With the exception of the app quitting, I
had all the exact same things happen. I could run XP on here, but it's
not worth it just for this. Seems like starting from scratch may be
the only way to go with this app. I'll keep at it.

Help with slim jim nec model
 

Well, I've gotten a little farther... If Jeff or anybody that has
CoCoaNEC wants to take a look at this file, that would be great.

http://home.earthlink.net/~davepd/nec/

It's supposed to be a VHF log. I used an example file for an HF log to
compare it with and I think I have all the geometry for it right. But
it still doesn't run right. I know for a fact this antenna works in
the real world. Looking at the example log file, they only had the
smallest front element fed, which doesn't seem right to me, but that's
how I did mine. Maybe somebody has an idea how to feed all the
elements properly. The biggest problem is that the elevation pattern
is extremely spiked and the SWR is off the scale. Not sure what I'm
doing wrong.

On the slim-jim one... I have the basic wire shape, but I can't figure
out how to break the element in the right place on the stub side.

Dave

Has this problem been resolved as of this date?

You just need some models to look at/dissect you can use mine.
I use 4nec2 it's free and more powerful than any other modeling program I've found pretty user friendly to.

http://ghz24.freeshell.org/antenna/models/elevenmeter/
There are other antennas in the parent folder.
The link to your model is down if you send it to me or post it I'll take a look.
Here is a pretty nice LPDA I can't take credit for it though.
It demonstrates proper feeding of an LPDA

CM 8 ELEMENT LPDA by "old sparks"

CM 470-810 MHz

CE

GW 1 21 0 -0.158 0 0 0.158 0 0.00081

GW 2 21 0.055 -0.141 0 0.055 0.141 0 0.00081

GW 3 19 0.104 -0.126 0 0.104 0.126 0 0.00081

GW 4 17 0.147 -0.113 0 0.147 0.113 0 0.00081

GW 5 17 0.186 -0.101 0 0.186 0.101 0 0.00081

GW 6 15 0.221 -0.090 0 0.221 0.090 0 0.00081

GW 7 15 0.252 -0.080 0 0.252 0.080 0 0.00081

GW 8 13 0.280 -0.072 0 0.280 0.072 0 0.00081

GE 0 0 0.

EX 0 8 7 00 1. 0.

FR 0, 96, 0,0, 470, 5

PT -1

TL 1 11 2 11 -125 0. 0. 0. 0. 0.

TL 2 11 3 10 -125 0. 0. 0. 0. 0.

TL 3 10 4 9 -125 0. 0. 0. 0. 0.

TL 4 9 5 9 -125 0. 0. 0. 0. 0.

TL 5 9 6 8 -125 0. 0. 0. 0. 0.

TL 6 8 7 8 -125 0. 0. 0. 0. 0.

TL 7 8 8 7 -125 0. 0. 0. 0. 0.

RP 0 1 10 1510 90. 0. 0. 20. 0. 0.

EN