"Bob Bob" wrote in message
...
On a learning curve here. I'll admit I am after a fast answer or two.

Using 4nec2 to model what will likely be a 2m antenna used at the home
QTH. Its an extended double zepp. ie two 5/8's in phase with a hairpin
like centre section, the whole thing made of 1/2" copper and fed at 200
ohms with a 4:1 balun or 100 ohm Q section. I have also included the mast
but havent really adjusted for best gain. There will be a quad on the
other side that isnt modeled yet.

Looking good so far but;

- Is the diameter of the source wire an issue?

- How do I allow for the use of copper pipe 90 degree elbows used in
construction. If I model them as (say) a extra single wire at 45 degrees
to mimic the radious I run into segment len/diameter limits.

Any thoughts or feedback welcome. Nec file attached inline. (Apologies for
the line breaks) I have yet to go through convergence testing and playing
with numbers of segments in the shorter sections.

Cheers Bob W5/VK2YQA

CE
GW 1 13 0 0 15.19 0 0 16.38 0.012
GW 2 3 0 0 16.38 0.28 0 16.38 0.012
GW 3 3 0.28 0 16.38 0.41 0 16.38 0.012
GW 4 1 0.41 0 16.38 0.41 0 16.45 0.012
GW 5 3 0.41 0 16.45 0.28 0 16.45 0.012
GW 6 3 0.28 0 16.45 0 0 16.45 0.012
GW 7 13 0 0 16.45 0 0 17.64 0.012
GW 8 1 0.28 0 16.45 0.28 0 16.38 0.012
GW 9 81 0.501 0 0 0.501 0 17.7 0.025
GE 1
EK
EX 0 8 1 0 1 0
GN 2 0 0 0 14 8.e-3
FR 0 1 0 0 146 0
EN

Bob, while your model does not produce any errors with NEC 2, the
"Average Gain Test" (AGT) returns:

Freq.(MHz) Wavelength(m) Avg. Power Avg. Power (dB) Comments
-------------------------------------------------------------------------
146.00000 2.05340 0.78364 -1.05885
Questionable

All GW cards return a warning: " Seg.Len/Rad 8. Also the pole
segmentation is considered too large.

It appears that accurate modelling of such a structure in NEC 2 is not
possible unless you reduce the size of your conductors.

73,

Frank