René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Odd errors in helix geometry","articleBody":"Long story short, I'm trying to build a helical antenna based on physical parameters. What I mean by this is that the user should be able to specify a desired frequency [MHz] which is then converted to wavelength [m] and used to build the antenna. For instance, the relationship between [the distance between each turn of the helix and wavelength](https://ham.stackexchange.com/questions/10127/what-is-the-turn-spacing-on-a-helix-antenna#:~:text=Add%20a%20comment-,1%20Answer,-Sorted%20by%3A).\r\n\r\nI wrote a function to specify this in more user-friendly terms:\r\n\r\n```\r\ndef create_helix(s=1, hl=3, a1=1.0, b1=1.0, a2=1.0, b2=1.0, rad=0.001, tagid=0,\r\n              segcnt=36):\r\n    '''\r\n    Generates a helix or spiral of wire segments.\r\n\r\n            Parameters:\r\n                    s: Spacing between helix turns\r\n                    hl: Total length of the helix\r\n                    a1: Helical radius (X) at z = 0 \r\n                    b1: Helical radius (Y) at z = 0\r\n                    a2: Helical radius (X) at z = hl\r\n                    b2: Helical radius (Y) at z = hl\r\n                    rad: Radius of the wire\r\n                    seg_cnt: Number of segments comprising the helix\r\n                    tag_id: Tag number assigned to all segments of the helix\r\n            Returns:\r\n                    object: \u003cPyNEC geometry object\u003e\r\n                    \r\n    NOTES:\r\n        * The segments generated by GA form a section of polygons inscribed within\r\n    the arc\r\n    \r\n    - If an arc in a different position or orientation is desired, the segements\r\n    may be moved within a GM card.\r\n \r\n    * Use of GA to form a circle will not result in symmetry  being used in the\r\n    calculation. It is a good way to form the beginning of the circle, to be\r\n    completed by GR, however.\r\n    '''\r\n    return context, geo.helix(s, hl, a1, b1, a2, b2, rad, tagid, segcnt)\r\n```\r\n\r\nOf course, this calls the `helix` function from PyNEC:\r\n\r\n```\r\n def helix(self, s, hl, a1, b1, a2, b2, rad, segment_count, tag_id):\r\n        return _PyNEC.c_geometry_helix(self, s, hl, a1, b1, a2, b2, rad, segment_count, tag_id)\r\n```\r\n\r\nAs a base use case, ```create_helix(s=1, hl=3, a1=1.0, b1=1.0, a2=1.0, b2=1.0, rad=0.001, tagid=0, segcnt=36)``` works fine. \r\n\r\n\r\n\r\n____**ISSUE 1**____\r\nIf I use a desired frequency of 400 MHz, this is equivalent to a wavelength of 0.749 meters and results in a vertical separation between turns for the helical antenna (S = 0.225*wavelength) of 0.225 * 0.749 = 0.1685. Plugging `S = 0.1685` into the previous use case:\r\n\r\ncreate_helix(s=0.1685, hl=3, a1=1.0, b1=1.0, a2=1.0, b2=1.0, rad=0.001, tagid=0, segcnt=36)\r\n\r\nresults in an error:\r\n\r\n```\r\nTraceback (most recent call last):\r\n  File \"/Users/apung/Documents/Repositories/antenna-modeling/src/radPattern_3d.py\", line 139, in \u003cmodule\u003e\r\n    geometry_module.define_excitation()\r\n  File \"/Users/apung/Documents/Repositories/antenna-modeling/src/geometry_module.py\", line 463, in define_excitation\r\n    return context.ex_card(extype, tagTheta, rnkPhi, pntRa, chkimp, vltTheta,\r\n  File \"/Users/apung/anaconda3/lib/python3.10/site-packages/PyNEC.py\", line 151, in ex_card\r\n    return _PyNEC.nec_context_ex_card(self, *args)\r\nRuntimeError: NO SEGMENT HAS AN ITAG OF 1\r\n```\r\nIn fact, I get the same error for a value of `S = 0.99`, but the simulation run fine with `S = 1.0`.\r\n\r\nWhat's causing this? I read through the NEC documentation and the PyNEC documentation, but nothing seems to explain the units well.\r\n\r\nAdditionally, is there a way I can extract the (X,Y,Z) points of the 36 components that comprise the helix within the `context` geometry?\r\n\r\n\r\n\r\n____**ISSUE 2**____\r\nFor a moment, let's accept that `S` simply needs to be greater than 1 to get a working helix. The documentation also states that the helix can be made into a spiral by setting the height (`hl`) equal to zero. However, this also seems to be broken, because\r\n\r\n`geometry_module.create_helix(s=1.5, hl=0, a1=a1, b1=b1, a2=a2, b2=b2, rad=0.001, tagid=0, segcnt=36)`\r\n\r\nresults in the following error:\r\n\r\n```\r\nTraceback (most recent call last):\r\n  File \"/Users/apung/Documents/Repositories/antenna-modeling/src/radPattern_3d.py\", line 134, in \u003cmodule\u003e\r\n    context.geometry_complete(0)\r\n  File \"/Users/apung/anaconda3/lib/python3.10/site-packages/PyNEC.py\", line 148, in geometry_complete\r\n    return _PyNEC.nec_context_geometry_complete(self, *args)\r\nRuntimeError: Geometry has no wires or patches.\r\n```\r\n\r\nI would really appreciate any work-arounds and explanations on either of these issues, because I'm at a loss and I cannot seem to find anything in the documentation .","author":{"url":"https://github.com/aeropung","@type":"Person","name":"aeropung"},"datePublished":"2023-06-21T18:58:48.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/27/python-necpp/issues/27"}