cocoaNEC 2.0 Reference Manual (Section 3)
Kok Chen, W7AY [w7ay (at) arrl (dot) net]
Last updated: January 10, 2011
If you select New Model (or Command N) in the File Menu, cocoaNEC will open a new spreadsheet window with the name Untitled Antenna-N, where N starts with 1 for the first window that you open.
If you select Save in the File Menu while a spreadsheet window is still untitled, cocoaNEC will use the same mechanism as a Save As... .
Save As... presents you with a Save File dialog for you to select the folder and file name to save the model to. The model is saved as a file that can be opened using the Mac OS X Property List Editor (the Property List Editor application should be on the Developer Disk that came with the Mac OS X disk set). The default extension for a model file is '.nec'.
If the spreadsheet window has previously been saved, or you have opened the window from an existing .nec file by using the Open Model menu item, Save will update the model file without prompting with a dialog.
The spreadsheet comes with some auxiliary windows (Environment, Variables, Transforms, Networks, Output Control) in the form of sheets that drop from the title bar of the window. You can open the sheets using the row of four buttons towards the bottom left of the spreadsheet window. Subsequent sections will discuss the sheets in detain. You can navigate to them by using the second row of tab buttons at the top of this page.
The spreadsheet at the top half of the spreadsheet window is where you specify the geometry of the antenna.
As with the case of the Variables table, you add and remove elements of the antenna by using the + (plus) and - (minus) buttons below the table.
The + (plus) button has a contextual menu to add elements other than a simple wire. But by right clicking (or control-clicking) on the button, you can bring up the contextual menu to select which type of element geometry to add:
If you left click instead of right click on the + (plus) button, the new element will default to the Wire element.
When a new element is created, the new spreadsheet row will be empty except for the column that is under the # symbol. You can bring up the Element Inspector window for any element by double clicking on its number in the # column. The following figure shows the Shape (geometry) panel of the Element Inspector:
You can also open the Element Inspector for a wire by first selecting its row in the spreadsheet (a single click on the spreadsheet row) and then going to the Window menu in the Menu Bar and selecting Open Element Inspector (or using the Command-E keyboard shortcut).
A wire's "shape" has two endpoints, each with an (x,y,z) cartesian coordinate. It also has the radius of the wire and the number of segments you are assigning to this element. Each of these field will take a formula.
Notice that when you enter a formula into one of the fields in the wire element geometry (remember to hit the return key when you are finished with the formula), the evaluated value of the formula will appear in the corresponding column in the spreadsheet.
As an additional short cut, you can also edit the wire parameters directly from the spreadsheet without opening the Element inspector.
If you double click on a wire element's cell in the spreadsheet, cocoaNEC makes a copy of its formula and places it into the Cell Editor that is above the spreadsheet. The following figure shows an inactive Cell Editor:
The following figure shows an active Cell Editor after the "z" cell of the first endpoint of the wire is double clicked:
Notice that the Cell Editor's caption turns from "Edit" to a red "z1" indicating that the editor is actively editing the z component of the first endpoint of the wire. When you finish editing by hitting the return key, the evaluated value of the formula will appear in the spreadsheet cell, and the Cell Editor formula will be transferred to the cell's formula in the Geometry Inspector.
Please note that this direct editing feature is only available for wire elements. For other types of elements, you can only edit the element's parameters from its geometry inspector. For these other element types, only the type name of the element appears in the spreadsheet, as seen below for a spreadsheet that has one wire element and one arc element:
The except is the transform column. You can always directly enter a Transform variable by directly selecting its cell (you can of course enter it in the Element Inspector of the element).
Both cocoaNEC and NEC-2 keep the dimensional information in meters.
When the numbers are evaluated from their formulas and displayed in the spreadsheet cells, you have the option of displaying it in Metric units (default), in English units, in mixed English units or as a fraction of a wavelength. This is done by selecting the units in the Display menu that is below the spreadsheet. Notice that this does not affect how you have entered the formula nor the internal representation, it only affects the displayed result.
With the Metric display, the numbers will appear in meters. If the numbers are small, they will appear in centimeters and you will see a "cm" after the number. If the numbers are even smaller, they will appear in millimeters, with a "mm" after the number.
In English units, the number will appear as decimal numbers of either feet or inches. Small numbers will appear as inches. The numbers will have "ft" or in" after them.
In Mixed English units, the numbers will appear as an integer in feet, and if there is a fraction leftover, it will appear as a decimal number in inches. For example, a value of 12.54 feet in English units will appear as 12' 6.5" in Mixed English units.
Finally, you can display the numbers in units of the current wavelength, where the wavelength corresponds to the frequency that is defined in the Environment window.
You can switch between displayed units at any time and cocoaNEC will recompute and refresh the cells in the spreadsheet for you. If you change the frequency in the Frequency field, cocoaNEC will also update the spreadsheet cells. cocoaNEC will also recompute and refresh the display when you change any of the variables in the Variables table.
When the Run button is clicked, cocoaNEC will generate the NEC-2 input deck for the model that you have entered. The geometry elements in the spreadsheet, the variables in the Variable table, the frequency and ground parameters in the Environment window, the networks that are defined in the Network window and the output parameters in the Output Control window all affect what gets generated for NEC-2.
The "deck" is sent then to the NEC-2 engine for processing. cocoNEC then extracts the results from the output from NEC-2 and opens the Output Window to display them.
You can also run the active model by selecting Run Model (command R) in the Model Menu instead of using the Run button. If there is more than one model window open, the active model is the model whose window is active,
View as Formulas
When you enter a formula into a spreadsheet cell, it will show up as the evaluated number. You can look at the spreadsheet as cells of formulas instead, by selecting the menu item from the Model menu (seen in the preceding figure). The figure below shows a spreadsheet when viewed as formulas.