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tmolteno / necpp

NEC2++ is a C++ rewrite of the Numerical Electromagnetics Code (NEC-2) with many new features like automatic error detection when you specify the structure incorrectly and much faster execution. Nec2++ can analyse radiating as well as scattering properties of structures. The simulation engine in Nec2++ is compiled into a library for easy integration into automatic antenna design systems or GUI tools. Examples are included for using Nec2++ from C/C++, Ruby and Python.
http://elec.otago.ac.nz/w/index.php/Necpp
GNU General Public License v2.0
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Helix geometry ignores ITAG value #36

Closed kaklik closed 8 years ago

kaklik commented 8 years ago

Hello,

I have designed an antenna model with helical wires, but GH card input seems to ignore ITAG number of helix. Therefore I am unable to feed helix directly by excitation source.

Here is the NEC code, the output of nec2++ follows.

CM Helix and screen reflector for 143.05 MHz CE End Comments GH 1 50 1.29700E+00 6.48500E-01 1.62100E-01 1.62100E-01 1.62100E-01 1.62100E-01 2.00000E-02 GM 1 3 0.00000E+00 0.00000E+00 9.00000E+01 0.00000E+00 0.00000E+00 0.00000E+00 1.00000E+00 GW 10 2 0.00000E+00 0.00000E+00 6.48500E-01 -1.62100E-01 0.00000E+00 6.48500E-01 1.00000E-02 GW 11 2 0.00000E+00 0.00000E+00 6.48500E-01 1.62100E-01 0.00000E+00 6.48500E-01 1.00000E-02 GW 12 2 0.00000E+00 0.00000E+00 6.48500E-01 0.00000E+00 -1.62100E-01 6.48500E-01 1.00000E-02 GW 13 2 0.00000E+00 0.00000E+00 6.48500E-01 0.00000E+00 1.62100E-01 6.48500E-01 1.00000E-02 SP 0 1 -1.00000E+00 -1.00000E+00 -0.1 1.00000E+00 -1.00000E+00 -0.1 0.00000E+00 SC 0 0 1.00000E+00 1.00000E+00 -0.1 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 GE 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 EX 0 1 1 0 1.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 EX 0 2 1 0 0.00000E+00 1.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 EX 0 3 1 0 -1.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 EX 0 4 1 0 0.00000E+00 -1.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 FR 0 5 0 0 1.40000E+02 1.00000E+01 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 RP 0 25 50 0 0.00000E+00 0.00000E+00 5.00000E+00 5.00000E+00 0.00000E+00 0.00000E+00 EN 0 0 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00

nec2++ -i QHA_Bolidozor_patch.nec QHA_Bolidozor_patch.out NEC++ Runtime Error: NO SEGMENT HAS AN ITAG OF 1

ytakeyasu commented 8 years ago

Hi,

This issue is related to: Version 1.7.1 Changed API of c_geometry::helix() to put the tag id and segment count at the start.

c_geometry.cpp: 450 helix( xw1, yw1, zw1, xw2, yw2, zw2, rad, card_int_2, card_int_1); may be 450 helix( card_int_1, card_int_2, xw1, yw1, zw1, xw2, yw2, zw2, rad);

also nec_context.cpp: 355 m_geometry->helix(s, hl, a1, b1, a2, b2, rad, segment_count, tag_id); may be 355 m_geometry->helix(tag_id, segment_count, s, hl, a1, b1, a2, b2, rad);

By the way, it seems your model is violating NEC2's modeling rule "wire to be attached to a surface at patch center". To follow this basic rule, you may need multiple smaller surface-patches instead of single large patch. Take a look at the Example 6 of NEC-2 Manual, Part III: User's Guide.

Regards.

Yoshi Takeyasu

tmolteno commented 8 years ago

Thanks for the feedback. I've modified the helix code and will commit shortly after a little testing.

Kind Regards Tim