_getstarted.txt

zip contains tool for Antenna Modelling with examples

Getting started with the 4NEC2 version 5.6.0 visualization and optimization tool for NEC-2/4.

(latest update: Jan 24, 2006)

Note:	You can push F1 when a certain form/window is active to get context sensitive help for
	the particular window/form.

Content:

1) Create an antenna model using 'Geometry Edit'.
2) Show structure; generate data and view currents and phase distribution.
3) Generate Far-field data and view 2D polar and 3D far field patterns.
4) Generate frequency loop graphical-data.
5) Optimize antenna performance.
6) Sweep antenna variables.
7) Generate and view Near-field data.
8) Generate and use ItsHF Area-Coverage propagation data.
9) Generate and use ItsHF point-to-point propagation data.
	
	Before starting this tutorial, note that there are two different ways of using the 
	4nec2 program. The first way is recommended for the starting modeler and uses the 
	drawing-style 'Geometry editor' to create or modify an antenna model. This method 
	however does not allow the user to directly use the traditional- and/or genetic-
	optimizer functions.

	To use the optimizer or sweeper it is required that the model includes at least 
	one variable (SYmbol) to optimize. These variables however can only be specified using 
	the 'Notepad' or 'NEC' editors. How to specify and use SYmbolic information is descri-
	bed in the items 2 to 8 below

	For these items 2 to 8 it is helpful if the reader has some basic knowledge about 
	modelling 3-dimensional wire structures, using Nec-2 or Nec-4. Especially the use
	of GW, EX, FR and LD cards. Information's about this can be found in the initial
	pages of the Nec-2 user-manual available on the Internet at 
	www.qsl.net/wb6tpu/swindex.html.


1) Create an antenna model using 'Geometry Edit'

	As a starting-point we will create a basic 20-meter dipole fed with 50-ohm feedline.

	To show none-metric unit usage we consider ourselves for a moment as an US-citizen 
	using Inch and Feet as the basic length unit....

	The below specifications apply:

	- antenna height 	70 feet
	- wire length		33.7 feet
	- wire radius		#12 AWG
	- feedline length 	69 feet	(electrical length)

	First we open one of the existing example files (e.g. 36dip.nec). If not already 
	done so, specify 'Geometry Edit' as the prefered Edit method using the 'Settings' 
	menu on the 'Main' window. Furthermore select 'Feet' as the length-unit and 'Inch/Awg'
	as the 'radius-unit' using this same 'Settings' menu.

	When done, select 'Edit -> Input-file' on the 'Main' window or use the <F6> key to 
	start 'Geometry-edit'. A picture of the selected example file is displayed. If not 
	already set, select 'Options -> Set Segmentation -> Medium' on the Edit window to set
	medium segmentation density

	To create a new model, Select 'File -> New' on the Edit-window.

	*) Setting design frequency

	When starting a new model, initially on the lower right,  frequency 'data' is displayed. 
	This because one of the first things we will have to do is specifying the antenna 
	design-frequency. Enter 14.15 (MHz) in the 'frequency' text-box on the right part of 
	the window. When entered, click the 'wire' button on top of the window (the one with
	the single line in it). Notice the grid-size changing from .025 to .5 feet, correspon-
	ding to about half a wavelength for the window-width. Furthermore the default 3D-
	display view is now set to 2 dimensional XZ plane. (The Y-axis is pointing backwards)

	*) Add new wire(s)

	To start adding a new wire, click the 'Add' button. The mouse-pointer changes to a
	cross-hair, indicating 'Add-mode' is activated. The Y-position text-box on the right
	is now highlighted. If required you can specify a certain 'depth' position, but for
	now we will stay in the XZ-plane for an Y-position equal zero.

	When you will try to locate a mouse-pointer position for which the height Z equals 
	70 feet, you shouldn't succeed, because the grid-size is too small to cover a Z posi-
	tion of 70 feet. 
	First increase grid-size to 1 feet by clicking on the left arrow for the 'Zoom' 
	scroll-bar. When done, point somewhere inside the picture-box (that part of the 
	window where the antenna structure is displayed), hold down the right mouse-button
	and move the X-axis to almost at the bottom of the picture-box. Now you should be
	able to locate a position for which Z equals 70 feet somewhere in the upper region
	of the picture-box.

	Because we want to create a line at Z=70 feet with a length of 33.7 feet we will
	have to locate a point for which Z = 70 and X = -33.7/2 = 16.85 feet. However, 
	because the 'Snap to grid' box is checked you won't succeed in this. For now we 
	will locate a position for which X equals -17 feet.

	To start drawing the wire, click and hold down the left mouse-button and drag the 
	mouse-pointer to the second position for which Z=70 and X=17 feet, then release the
	mouse-button. Because this is the first wire added to the model, a pop-up window is
	displayed asking for the initial/default wire diameter. Use the supplied default of
	.05 inch.
	Now the first wire, the dipole itself, is created. On the right of the picture-box
	all data belonging to this wire is listed. You can edit the end-1 or end-2 coor-
	dinates text-boxes to further refine the end positions. You will also notice that
	the number of segments is set to 25, corresponding to 'medium segmentation'.

	The second wire, to connect the other end of the feedline, is done the same way by 
	drawing a line from x=-1 to X=+1 for a height Z=1. This second wire is automatically
	divided into 3 segments. Because we only need this wire to attach one end of the 
	feed-line, manually change the number of segments to 1. 

	Don't worry in case you did not position the wire-ends at the right coordinates. To
	move wire-ends, click the 'pointer' button and place the mouse-pointer on the wire-
	end to move. The mouse-pointer should now change to four-arrows, meaning you can move
	the wire end. Hold down the left-mouse button and move the wire end to the required
	position. As an alternative you can also directly edit the end-1 or -2 XYZ values.

	*) Add feed/transmission-line(s)

	Next we will have to add the feedline. But, before doing so we need some knowledge
	about how wires are identified in Nec-2/4. All wires are assigned a unique tag-nr.
	Mostly the tag-number equals the wire-number. Ater delete, copy or paste operations
	however this sequence may have changed. Tag-numbers should still be unique. You may
	use 'Resequence tag-numbers' in the 'Option' menu to make tagnumbers equal to the 
	corresponding wire-numbers again.  

	Each voltage/current-source, transmission-line or RLC-load (see below) is 'assigned'
	to a wire using this unique tag-number. To specify the position of the source, TR-
	line or load on the specified wire a segment-number between 1 and the nr-of-segments
	for the wire is used.  

	Using Geometry-edit these tag- and segment-numbers are automatically assigned. It is
	allowed to change these number manually. When doing so please note how these tag- and
	segment-numbers are used within Nec-2/4.
	 
	Adding/creating a transmission-line is done by clicking the 'TR-line' button (the 
	one with the ladder picture). If not in 'Add-mode', click the 'Add' button to start
	adding a new Tr-line. Locate the mouse-pointer on the middle of the first wire and
	click and hold down your left mouse-button and move the mouse-pointer to the middle
	of the second wire. When reached release the mouse-button.
	When positioning was not too rude a new transmission-line is now added. If not, try
	again. Note also that we did not take the velocity-factor into account, we just used
	an electrical length of 70-1=96 feet.

	*) Add voltage source

	To prevent loosing the changes, backup the model using 'File->Save as' and choose a
	folder- and file-name for your new model.

	The next thing to do is add a voltage-source. While still in Add-mode, click the 
	'Source button' (right of the 'Wire button'). Next click and hold down your left 
	mouse-button somewhere in the picture-box. At the current mouse-pointer position a
	new source-object is displayed. Drag the source-object to the middle of the second
	wire, just between the two lower wires-ends of the feedline and release the mouse-
	button. When properly positioned a new source is now added. If not try again.

	For now we will set a default voltage-source of 1+j0 volt (1V @ 0 deg.)

	Select the 'pointer' button to switch back to select-mode mode. The mouse-pointer
	changes to the default arrow-pointer indicating 'Select-mode' is active.

	*) Add wire-conductivity

	We use copper wire for our antenna, so we will have to include this in our model 
	(the default is perfect wire with zero losses). To do this, click the 'Loading 
	button' (the one with the RLC symbols), click somewhere in the picture-box and drag
	the new load-object to any place on the first (upper) wire and release the mouse-
	button. The new load-object is now 'connected' to the first wire. 
	
	The default load however is a lumped load. To change this to a distributed/wire-load, 
	change the 'Par-RLC' selection for the Load-data on the right of the screen to 
	'Wire-ld'. The box shape on the first wire should now have changed to a red line-
	segment. The initial conductivity is set to 10000 mho/m. Change this to 'Copper' by
	using the 'G (mho/m)' selection-box on the right of the picture.

	To specify wire-conductivity for the whole structure, first change from 'spot load'
	to 'single-wire' (see lower right) . Notice how the whole wire becomes 'wire-loaded'. 
	Next change to 'Whole struct'. The 'Wire-conductivity' is not visible any more. This 
	would not deliver us additional information because the whole structureis now loaded
	(both wires). To enable wire-loading display for the complete structure use 'Option 
	-> Show wire loading'.

	For now we have added all required objects. Switch back to 'Select-mode'.

	*) Select/move objects

	The attentive user will have noticed that we did not yet explicitely specify our 
	wire radius (half the diameter). We will do so now. While in 'Select-mode', click
	the wire button and select the upper wire (wire 1). The wire color will change to 
	red (if not already set), indicating this wire is selected for modification.  In the
	wire-data on the right part of the screen select #12 as the wire-radius for wire 1. 
	Select wire 2 and change the radius also to #12.

	Also click the 'Trans-line' button to set the 'Char-Imp./Z0' to 50 ohms.

	To move a wire, click the 'Wire' button again and select the required wire. When the
	mouse-pointer is over the selected wire the pointer changes from the default to a
	two-point or four-point indicator. When a two-point indicator is visible one can 
	move the whole wire at once. When a four-point indicator is visible one can move the 
	corresponding wire-end. Move a wire(end) by clicking on the wire(end) and hold down 
	the left mouse-pointer while dragging it to a new position and releasing the mouse-
	button.

	When XY, XZ or XY plane (2D) is selected you can move a wire(end) to any place 
	inside the picture-box. When 3D-view is selected however be careful with this, 
	because a moved wire(end) automatically connects to the another near wire-end. To
	undo the latest move-action use the 'Edit' menu or move the mouse-pointer over the
	wire(-end) till a two/four-point mouse-pointer becomes visible and click the right
	mouse-button. A pop-up window is now displayed in which you can select 'Undo move'.

	The same principles apply for moving sources, loads and transmission-lines. However 
	these objects can only be moved from one wire(segment) to another wire(segment).

	You can textually change/edit XYZ-, wire-, tag- or segment-position by selecting the 
	required object and modify the 'object' data on the right of the screen.

	If required, backup or save your model by using 'File->Save(as)' to be able to 
	restore a previous model in case you made a serious mistake.