†The utility "NEC-2 for MMANA" is intended for calculation of antenna models made and optimized in program MMANA. Calculation is made with use of† NEC-2, including calculations above a surface of the ground in Sommerfeld-Norton model, calculations with use NEC-2 Extended Thin Wire Kernel (EThWK) and voltage excitations by Current Slope Discontinuity Voltage Sources (CSDVS). Also in "NEC-2 for MMANA" it is possible to make calculation in a case when some wires in MMANA model are in dielectric isolation. A maximum quantity of processable segments Ė 3000, NEC-2 engine compiled by Arie from Neede, Netherlands. All files of the program are placed in one directory, program must be used only as 32-bit windows application.
"NEC-2 for MMANA" reads a file created MMANA with expansion *.maa, and converts it in acceptable for calculation on NEC-2 the form. Restrictions at converting the following:
Segmentation for NEC-2 calculations.
For calculation in NEC-2 the establishment of segmentation occurs as follows.
With parameters of segmentation in MMANA "-1", "-2", "-3" establishment of segmentation for NEC-2† ("DM2 seg" is switched off) frequently turns out unfairly dense, that increases in "NEC-2 for MMANA" time of calculation over necessary. Also the common number of segments can become more allowable, limited used version NEC-2, and the length of segments can become too small for accurate calculations.
Calculation above real ground.
"NEC-2 for MMANA" sets for calculation external conditions for antenna models (Free Space, Perfect Ground, Real Ground) according MMANA specification registered in corresponding *.maa file. For a case of the real ground the Sommerfeld-Norton model of the ground is established by default, however, if in MMANA model some wires are touching ground calculation with the Sommerfeld-Norton ground can not be made. In this case there is an opportunity to specify ground model as Perfect Ground.
Parameters of the real ground (dielectric constant and conductivity) via MMANA-file are not transferred. They are necessary to input manually in " NEC-2 for MMANA ". The surface of the ground is supposed in "NEC-2 for MMANA" unlimited and homogeneous.
Calculation of model of the antenna with wires in dielectric isolation.
The metal filament (vein) of wire is supposed as having the cylindrical form, isolation on it is located also as a cylindrical layer. MMANA model radii are encountered as radii of metal filament of wires. For taking in account of influence of isolation loading by additional inductance along all isolated wire is introduced with its thickening up to radius with isolation. Inductance calculated under the formula:
Where - radius of wire with isolation,
- radius without isolation,
- relative dielectric constant of isolation,
- velocity factor.
As before calculation †precisely is not known, but its values for practical cases of wire antennas on are not far from 1. For calculation it is assumed . Even at its value is 1 the accuracy of calculation is not lower than about 0.3-0.4 %. With value used in the program accuracy of calculation is really fit for practical use.
The given formula is derived under the assumption that , where - †a magnetic field around of wire (on an external surface of dielectric isolation, z - changes along a wire) and a current in wire, the length of wire also should be much more than its radius with isolation. For overwhelming majority of practical wire antennas these conditions can be counted fulfilled.
Idea of isolated wire calculation belongs to Alexander Yurkov, RA9MB and based on determination of surface impedance †at dielectric surface and boundary condition for fields on edge between medias.
"Find MMANA file".
This button user can find the *.maa file for calculation. Its name together with path is highlighted in the appropriate window.
By button "Refresh" model data of antenna in program are updated. This button is useful when working with antenna model proceeds simultaneously in MMANA and in "NEC-2 for MMANA". It is possible to make changes of model of antenna in MMANA and to save them in a file. If the name of MMANA file is not changed, by button "Refresh" the utility "NEC-2 for MMANA" updates earlier read data from MMANA a file. In the present version updating is necessary and is made for the data about an environment of the antenna, frequency and antenna height data, radii of MMANA model wires, sample of impedance for SWR calculation. Itís strongly recommended to use this button within all changes made in MMANA during simultaneous work with NEC-2 for MMANA and MMANA.
"Calculate at original of MMANA file".
By the button "Calculate at original of MMANA file" converting and calculation on NEC-2 is performed for models of antenna as it is given in *.maa a file. Results of calculation and the diagram can be looked on a sheet "RP plots" and "Table of results".
"Angles for radiation pattern calculation".
In a window "Angles for radiation pattern calculation" user can set an angles needed to calculate the azimuth diagram (elevation angle needed) and for the elevation diagram (azimuth angle needed).
In a window "Ground model" the type of the ground and its parameters are set.
"Dielectric coated wire calculations".
In the given window parameters for calculation of antenna with isolated wires are set, calculation is made by button "Calculate" and "Calculate with wires in dielectric coat" (sheet " Tables of results ").
In a field "Radius of wires to be coated" the radius of wires needed to be dressed in isolation (i.e. this radius should be one of designated in MMANA) is set. At calculations it is supposed, that one or several wires in MMANA have the radius appropriate to radius of a metal vein of an isolated wire, - these wires and will be coated in isolation. Radii of wires can be chosen from item list of this field.
In a field "Radius of wire with coat" the radius of a wire with isolation is set (radius of its metallic vein is set "Radius of wires to be coated").
In a field "Dielectric constant of coat" relative dielectric constant of isolation is set.
In a field Frequency" frequency of calculation is set. In this field value of frequency from MMANA file after calculation by the button "Calculate at original of MMANA file" appears.
In a field "Make all wires shorter on" (and scroll bar connected to it) sets how shorter it is needed to make ALL wires of antenna. At its difference from 0 all wires will be shorted for calculation, without dependence from their radius (i.e. without dependence all of them in isolation whether or not). Value of this field not changes contents of MMANA file.
Calculation is made by button "Calculate" or "Calculate with wires in dielectric coat" (on a sheet "Tables of results").
Making calculation several times at different frequencies it is possible to find resonant frequency for the antenna with wires in isolation.
If all wires in MMANA a file have identical radius all of them can be designed as isolated (this radius it is necessary to designate in a field "Radius of wires to be coated"). Then several calculations with different parameter in field "Make all wires shorter on" it is possible to find how wires must be geometrically shorter in isolation. If wires in MMANA have different radiuses (in isolation can be designed only separate of them) to change length of isolated wires better directly in MMANA and to make calculation in "NEC-2 for MMANA" with parameter in field "Make all wires shorter on" equal 0.
Sets in NEC-2 calculation with use of Extended thin wire kernel.
Sets in NEC-2 using Current Slope Discontinuity voltage sources as sources in antenna model. When this option is switched off the Applied E-Field voltage sources will be used.
On this option in a window on a sheet "Data sheet" NEC-2 input information is shown. No calculation performed, only translated on NEC-2 input language task for antenna model from *.maa file is shown. Buffer file (indata.txo) refreshed with this information.†
For a wire in MMANA segmentation such as "-1", "-2", "-3" program sets for calculation in NEC-2 linear segmentation with density DM1/lambda, i.e. with the greatest, offered MMANA, density of segments on a wire is given (if option "DM2 seg" is switched off). If† "DM2 seg" is switched on program sets segmentation with density DM2/lambda.
The sheet "RP plots".
On it diagrams (azimuth and elevation) and results of last calculation are shown. In a window with results it is possible to make remarks and comments. On Popup menu it is possible to save diagrams and results.
Through radio-buttons in a window "Polarization components" it is possible to sketch diagrams for polarization components of far field. In MMANA the component "Phi" is designated as horizontal, "Theta" as vertical.
Results of calculation are deduced also in a window on a sheet "Data sheet". It is possible to copy its contents to clipboard on a Popup menu.
The sheet "Table of result".
Results of calculations are composed in table form. User can change also frequency and height of antenna for further calculation after switching on corresponding options. Ground parameters also can be quickly changed. MMANA file will not be changed.
The sheet " NEC-2 input ".
In the left window ("Edit window") NEC-2 input code can be corrected and appended using most of cards allowed by NEC-2 input language. By using button "Start NEC-2" the contents of Edit window will be calculated, results will be shown also in output windows on sheets "Table of results", "RP plots", "Data sheet", in table on "Table of results", on far field plots.
By using "Read current NEC-2 input" the contents of buffer file (Indata.txo, current task for NEC-2 engine, "current NEC-2 input") will be loaded into Edit window. This is useful for easy correction of translated from *.maa file antenna model. Contents of Edit window can be saved in *.nfm file (NEC-2 code text file), contents of opening *.nfm file also will be loaded in Edit window.
Angles for radiation pattern calculation can be specified in corresponding fields of this sheet. Only RP cards in Edit window will be corrected.
"Read admittance" option is used to show in results of calculation values of admittance instead of impedances for sources. Itís useful when standard scheme for current sources defining (by additional NT card and special small wire far from base antenna wires) is used.
By using "Read NEC-2 output file" NEC-2 output file, Outdata.txo can be viewed after calculation (or error message) by standard Windows Notepad editor placed in Windows working folder.
The sheet "Currents in fields".
Near field calculations are possible using contents of Edit window or contents of buffer file ("current NEC-2 input"), Indata.txo. All step values must be >0. Results will be written (saved) in *.csv file, format is the same as in MMANA. Also results can be viewed in NEC-2 output file, Outdata.txo by "Read NEC-2 output file" in "NEC-2 input" sheet.
Numerical Green function (NGF) can be written also according task in Edit window or in "current NEC-2 input" buffer file. NGF file is placed in working folder of NEC-2 for MMANA and named as Ngf2d.nec. From this folder itís usually retrieved by GF card when one used for antenna model calculation in Edit window.
Plots for currents in wires also plotted in this sheet. Distance data shown in direction from first end of wires (begin of wire) in model to second end (end of wire). Currents table also can be saved in *.csv file, format is the same as in MMANA.
With button " NEC-2 wire geometry view " (also button "Viewer" and in PopUp menus, viewer may be poor working on 256-color system palette) antenna geometry viewer is started. Viewer based on information from NEC-2 output buffer (file Outdata.txo), so even wire structure contained in numerical Green function (if it used for calculation) will be displayed. Viewer must be started after antenna calculations. Currents in wires also can be shown. Phase of current is flipped if corresponding segment current phase <-90 deg. or >90 deg. Two bars in the left part of window rotate image in XY plane and along Z-axis. In above field number of wire (TAG)† may be selected and info about it will be displayed. Nearby double button zooms image. Double button in right of window may translate image along coordinate axis. Bar in right side will zoom currents shown.
Patches (if so present in NEC-2 model) will be displayed as small (1/4 of real square) quads; moving bar in left bottom corner can enlarge these. Pictured quads really marks computed surface and reflects its shape. If quad is colored as solid its normal is directed "to you", otherwise (only border of quad seen) its normal directed outward, "out of you".
Red dots on wires mark positions of voltage sources. For Applied E-field source dots placed in the center of corresponding segment. For Current Slope Discontinuity voltage sources dots also placed in the center of segments although really it present in the beginning of corresponding segment. Blue dots marks NT or TL ports (and also placed in the center of relevant segment). Yellow dots marks loads.
Alexander Yurkov, RA9MB for idea of dielectric coated wire calculations;
Ray Anderson, WB6TPU, and Arie from Neede, Netherlands for fine working NEC-2 engines;
Gary Goncharenko, DL2KQ for attention to work and useful advices,
Alexander Schewelew, DL1PBD, for ideas to improve graphics.
Dimitry Fedorov, UA3AVR