_getstarted.txt

zip contains tool for Antenna Modelling with examples

	logarithmic scaling. By default the pattern is normalized for maximum gain for the
	current Theta(elevation)/Phi(azimuth) angle. The Max-gain value is displayed in the
	upper left corner. To normalize against the overall maximum gain, press the <Home> 
	key. To disable all normalization, press the <Home> key again. A third push will 
	bring you back to the default state.

	To get the gain and angle for a particular point on the pattern it is possible to 
	select a point on the pattern line with the mouse and click the right mouse button.
	Use the 'I'(nfo) key or 'Show->Info' the get additional information about maximum
	gain, front to back ratio and beam-width.  By default the 'total field' is displayed,
	to view the other generated patterns use the ','(<) and '.'(>) key's.	

	Use the 3D-viewer/<F9> (4nec2X only) to view the far-field data in 3D perspective.


4) Generate frequency loop graphical-data

	In this third example the Example3.nec input file is loaded. In this file an
	inverted-V antenna for 80 meter is used. The top of this antenna is brought to
	a height of 20 meters, and a ground specification (GN card) is included.
	For easy reading, Tab characters are used to separate the different NEC card 
	values. If you take a look at the 4nec2 input file (F6), you will see three types 
	of 'GN' cards, two of them are preceded by a " ' " sign, so they are treated as 
	4nec2 comment. The other one (the GN 2) card is 'active', so in this example the 
	high accuracy Sommerfeld-Norton ground is used. A conductivity of 0.006 S/m and a 
	dielectric constant of 14 is used (average ground, see the 4nec2 help)   

CM Example 3 :   Inverted-V over average ground
CM               See _GetStarted.txt
CE 
SY hgh=20                               ' Height
SY len=20                               ' Wire length
SY ang=110                              ' Angle between sloping wires
SY Z=len*cos(ang/2), X=len*sin(ang/2)   ' Get delta-Z and -X distances
'
GW	1	20	-X	0	hgh-Z	-0.1	0	hgh	#12 ' radius for
GW	2	1	-0.1	0	hgh	0.1	0	hgh	#12 ' #12 wire
GW	3	20	0.1	0	hgh	X	0	hgh-z	#12
GE
'
'GN	-1                                              ' Perfect ground
'GN	0	0	0	0	14	.006    ' Finite ground
GN	2	0	0	0	14	.006    ' Sommerfeld ground
'
EX	0	2	1	0	1	0       ' Default voltage source
FR	0	1	0	0	3.680           ' Design frequency
'
EN							' End of file

	In this example the 'sin' and 'cos' mathematical functions are used to calculate
	the delta-X and -Z distances for the outer ends of both sloping wires.

	To generate frequency loop (frequency sweep) data, Enter the F7 key, and select
	'Use frequency loop'. With this calculation-option line-chart graphs are generated
	for Forward-gain, Front-to-Back ratio, Front-to-Rear-ratio, SWR and input impedance.

	When selecting this option additional input-boxes appear. For now we select the
	'Gain' option. Please enter a frequency start-value of 3.5, a stop value of 4 and
	a step-size of .02 Mhz. Enter a value of 90 for the Phi angle and a value of 55 for
	the Theta angle, and click the 'Generate' button.
	When calculations are done a third window is displayed called the 'Line-chart (F5)'
	window. In this window you can switch between "S"(SWR), "G"(Gain) and "I"(impedance)
	display. Use the "L" key to switch between linear and logarithmic Y axis scaling.
	Use the "F" key to change to X-axis scaling. By default the SWR, R-in and Z-in 
	graphs are set to logarithmic, the others default to linear. When linear scaling is
	set you can use the 'Up','Down', 'Page-up' and 'Page-Down' keys to move and zoom the
	graph. Use the 'Tab' key to select one or both graphs.
	
	4nec2 also has the possibility to display the input impedances on a Smith chart. 
	Enter the F11 key to select this option. Use the cursor keys to select a specific
	frequency. More experienced users may use the <Shift> key in conjunction with the
	cursor keys to 'add' a certain length of feedline. Use <Home> to (de)normalize.

	To view the changing for, for example, the vertical far-field pattern when fre-
	quency increases from 3 to 30 Mhz, please enter F7, 'use frequency loop' and select
	the 'Ver'tical option. Enter 3, 30 and .5 for frequency start, stop and step-size. 
	Again enter 55 for the Theta- and 90 for the Phi-angle of our direction of interest.
	Click 'Generate' and when calculations are done, you can 'walk' through the dif-
	ferent vertical far-field patterns on the 'Pattern' (F4) form with the 'Left' and 
	'Right' arrow key's.

	Note: 	Select the Nec2dSX engine for increased accuracy when running a frequency-
		loop using SomNec ground settings.
		
5) Optimize antenna performance.

	In this example again the 'Example3.nec' input file is used, but now we will opti-
	mize antenna-performance. As a first try we will use the traditional hill-climbing
	optimizer and optimize radiator length for resonance. To do this, start the Optimi-
	zer by entering the F12 key. A new window appears with a number of selection- and
	input-boxes. First we set the traditional optimizer by selecting 'Optimize' in the 
	Function-box and 'Default' in the Option-box. After this we select the variable(s)
	we want to optimize, by clicking on the 'len' variable in the list-box with the
	'variables' heading. The selected variable(s) will show-up in the right list-box.
	
	Furthermore you must select one or more antenna properties to optimize, together 
	with their "importance" (weighting factor, contributing in the total result).
	To optimize for resonance, please enter a value of 100 (%) in the 'X-a' box, 
	(all other values must be set to zero) meaning only the Reactive component con-
	tributes for 100% in the total result. (FOM, figure of merit). To get resonance, 
	this property must be minimized. This is the default for the 'X-a' property. (Click
	with the right mouse key on one of the property-boxes to change this default target)

	After clicking the 'Start' button the optimizing process starts and the button 
	text changes to 'Halt'.

	In the upper right box, the selected variables together with the direction and 
	relative amount in which they are changed are displayed. In the lower left box the
	calculated property values are displayed for each new optimization step, together
	with the calculated overall result (Res%) and the step-size used. 
	In the lower right box the corresponding variable value(s) is/are listed, so it is
	possible to follow the optimizing process.

	After some time the process should stop with the message 'Optimized in XX steps',
	indicating the optimization is ready. To premature abort the process, you may click
	the 'Halt' button. It is possible the process is not immediately halted. If so, 
	please wait till the active calculation step is ready. Sometimes it may be necessary
	to click the button once more. After the process is ready/aborted, you may change 
	the variables or properties and continue optimization by clicking the 'Resume'
	button.	

	If the optimization results are OK, you may use the 'Update NEC-file' button to up-
	date your NEC-file with the new variable value(s). Use 'Exit' to quit the optimizer
	without saving.

	In the same way you can optimize for Forward-Gain, Front-to-back- and/or Front-to-
	Rear-ratio. If one or more of these properties are selected, you must also specify
	the Forward-Gain and (for none default angles) backward-gain angle to calculate for.

	For quick optimizations, a resolution of "0" (zero) could be used. In this case 
	only the Gain for the specified Forward- and backward-angles are calculated and no
	additional Front-to-Rear data is calculated.

	For more precise optimizations, a none-zero resolution (e.g. 5 degrees) could be set.
	Now a complete 3D pattern is calculated for each optimization step, so the difference
	between the Forward lobe and the largest side-lobe in the backward 180 degree part of
	the pattern is calculated and displayed as the Front-to-rear ratio.

	If optimizing for Gain or F/B, one may also specify a delta Theta and/or Phi for the 
	forward- and/or the backward-angle. If a none-zero value is specified, the gain is
	averaged over the range between Phi - delta_phi and Phi + delta_phi. The same holds 
	for the Theta angle. 

	Mostly optimization is performed for total-gain. If required, however you may opti-
	mize for horizontal/vertical-gain or E-theta/E-phi. Optimization with included sur-
	face-wave is also possible. 

	Variable changes are reflected on the Geometry view. To view them, after starting
	the optimization process, please move and/or resize the optimizer window to the 
	lower left part of the screen. If optimization is done for Gain and a none-zero
	resolution is set, the far-field pattern changes are also reflected on the Geometry
	(if 3D pattern is enabled) and the Pattern form. The optimization steps are logged
	in the optimzer.log log-file. This file can be viewed with 'Show -> Optimizer log'
	in the Geometry window.

6) Sweep antenna variables.

	With version 5.3 and later it is possible to evaluate and graphically visualize the
	effect of antenna variable changes. To make this possible a variable-sweeping func-
	tion has been added in the Optimizer function box. If, after enabling the optimizer 
	window (F12), this Sweeper function is selected, the optimizer window changes a bit.
	For each selected variable the minimum (start) and maximum )stop) values to sweep
	between is displayed. YOu can manually change these min/max values. Furthermore a 
	'Nr of steps' input-box is displayed, with a default value of 10. 
	Using the 'Options' selection box ypou are able to select between the vertical of 
	horizontal or 3D far-field pattern.

	To evaluate the effect of changing antenna height from 20 to 30 meters, we use the
	'3el-inverted-V.nec' file. After loading this input file, start the optimizer/sweeper,
	select 'Sweeper' and select 'hgh' as the variable to sweep. This variable is now 
	added to the 'selected' list', default values of min = 10.5 and a max = 42 meters is
	set and a default number of 10 steps displayed. To sweep a height change from 20 to 
	30 meters select the 'hgh' value in the 'selected' list (click again if the variable
	is removed) and change the min and max values to 20 and 30.  

	Set the Theta- and Phi-values to 55 and 90 degrees to specify the angle for which
	Gain is calculated. Specify a resolution of 10 degrees. (If resolution equals zero,
	this will increase sweeping speed, however no pattern is calculated and displayed)

	Click the Start button to start the sweeping process. First of all an initial 
	step is made with the default height of 20 meters. After that 10 incremental steps
	are made in which each step the height is incremented by 1 meter.

	The resulting SWR, Gain, F/B, F/R, R-in, X-in and efficiency values for each step 
	are reported in the 'Calculated Results' box. The resulting horizontal far-field 
	pattern for each step is updated on the 'Pattern (F4)' and 'Geometry (F3)' window.

	If all steps are done, you may use the 'Exit' button to close the optimizer/sweeper
	window or change/add/remove variables, change settings and/or proceed with another
	range of steps, by clicking the 'Restart' button.
	
	After closing the window, all results for the last sweep are reported in the line-
	chart graphs on the 'F5' form. The horizontal or vertical patterns (according your
	selection) for the different calculation steps composing the sweep are available on
	the 'Geometry (F3)' form. Use the Right- and Left-arrow-key's to switch between 
	steps. Use the 'Show Log' button to view or print the last sweeper results.

	Note however that as distinct from the default 4nec2 operation, the sweeper
	results are only stored in memory, and not in a NEC output-file. So, if 4nec2 is
	left or the input file is viewed or another 4nec2 file is selected. The sweeper
	results are lost. The log-file is kept as long as a new optimization or sweep is 
	done. 

7) Generate and view Near-field data

	As an example to generate near-field data, the file NearFld.nec is included in
	the package. To use this example, please load this file and push the F7 key to
	get the 'Generate' window. Select 'Use original file', to start the calculation.
	This input-file already contains the required NE card is, so it is not yet 
	necessary to specify any near-field parameters. Calculations will take some time,
	because almost 30.000 near-field points are calculated. 

	When calculations are done, the Pattern windows is displayed with the 'Near-field'
	lay-out. Initially you mostly will see a blue plane with on the left a color-bar
	telling on the left, telling you what field-strength is represented by a certain 
	color. The maximum value will be in the range > 1e+4 volts/m. This is due to the
	fact that one or more of the calculation points will be very close (or maybe on) a