4nec2 main window

(1) The front-ends task to provide a useful editor for the antennas geometry (4nec2 'NEC editor')

(2) Prompting a command to the kernel (4nec2 'Calculate / Generate window') Here: to compute the Far Field Radiation Pattern

(3) Calling the kernel (button 'Generate')

When doing a computation we see 4nec2 calling up the NEC Kernel through this popup DOS console window.
Which holds a line showing the internal names of the input and output file to and from the kernel
and what kernel (here nec2d) is called up

(4) The front-ends task of interpreting the kernels output in a useful way (4nec2 'Pattern' window)

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4nec2 is programmed by Arie Voors.

From his website: The maximum number of segments, wires, field points, exitations / sources is a virtual one in 4nec2.
The user can edit these settings up to the amount of memory the machine 4nec2 is running on can handle.
The kernel in use has its own limitations too. The standard nec2d & nec2dSX kernels handle max. 11,000 segments.

I can for instance run a 4 bay of 26 element DJ9BV BVO Yagis containing 2236 segments in 132 wires just like that, engaging the enclosed nec2dXS kernel with max.-No. of nec LD cards set to 256 instead of default setting of 64 cards. Which the full version of EZNEC v.5 or 6 will not do as they are limited to 500 segments.

There is an online help for 4nec2 holding explanaintions and a number of PDF files. Amoung these is the 'A Beginner's Guide to Modeling with NEC' by L.B. Cebik, W4RNL, QST Nov. 2000

(1) EZNEC wires window as the front-ends geometry editor

(2) Prompting a command and calling the kernel, the first is integrated into the main window (button 'FF Plot');
the second is running in the background = hidden from the screen

(3) EZNEC plot window as the kernels output interpreter

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EZNEC v.5 and v.6 feature the nec2 kernel.

EZNEC is produced and sold by W7EL.
The demo version of EZNEC v.6.0 is limited to handle 20 segments, the full v.5.x and v.6.0 versions up to 500 segments.
There is a pro version, EZNEC Pro (also referred to as EZNEC+) available that handles 2000 segments and uses the nec4 kernel.

(1) MMANA 'Geometry' page as the front-ends geometry editor

(2) MMANA 'Calculate' page

(2) Prompting a command and calling the kernel, the first is integrated into the "Calculate" page (button 'Start');
the second is running in the background = hidden from the screen

(3) MMANA 'Far Field Plots' page as the kernels output interpreter

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MMANA features the mininec version 3 kernel. It is brough to you by JE3HHT, DL2KQ and DL1PBD.
The free basic version handles up to 8192 segments or 512 wires.
There is a pro version availabe. It handles 45000 segments, 10000 wires and 300/500 sources, provided you have +16GB RAM

There is an online help for MMANA basic at http://gal-ana.de/basicmm/en/

most about TANT is described on my website about Antenna Temperature

Read more on how to derive a NEC model for TANT in the official TANT Manual (PDF)

Here are 2 applications of TANT produced by Vladimir, UR5EAZ

For any standard application of TANT at zero elevation T_antenna = (Tsky + Tearth) / 2 so that independently of the antennas pattern,
a constant T_ant is the outcome. But what if we tilt the Yagi by 90 degrees of elevation in a theoretical experiment?

Now former T_sky and T_earth become 'T_front_boresight_of beam' and 'T_rear_lobes'. With this change a number of antenna parameters
useful for studying its suitability for terrestrial weak signal communication can be derived. Former T_sky now is the Brightness Temperature of the sphere that lies in beam direction, while former T_earth becomes the Brightness Temperature of the rear sphere.

(1) The 'Ratio of Radiation Power into Rear Semi-Sphere to Radiation Power into Sphere' MS Excel

This table holds 50, 144 and 432 MHz Yagi-Uda antennas

Download UR5EAZ's MS Excel 'RRF_dB_october.xls' (the file contains step-by-step instructions)

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UR5EAZ produced a second interactive MS Excel table. It shows Antenna and System G/T. In here the user can edit T_earth, T_sky, RX NF and bandwidth while the numbers for System G/T adapt.

(2) The 'Unusual application of the TANT program' MS Excel
in which T_sky, Tearth and also RX bandwidth and NF can be edited and G/T and System NF are being computed.
This table holds 50, 144, 432 and 1296 MHz Yagi-Uda antennas at an elevation of 5 and 30 degrees

Download UR5EAZ's MS Excel 'INTERACTIVE_TABLE_JANUARY_17.xls' version 2.3

Vladimir likes to thank Lionel, VE7BQH and Hartmut, DG7YBN for consulting and verifying of the calculation

2016-07-05: Vladimir updated his Excel by adding a calculation of expected level of own EME echos when transmitted and received with
a chosen Yagi at a filled in ouput power and RX Noise Figure. A practical number in practise.

Download UR5EAZ's MS Excel 'INTERACTIVE_TABLE_JULY_5_2016_ECHO_SNR' version 2.9

It reads files of 3D Far Field plots produced with MMANA
and computes Gain, Forward-, Sidelobe-, Backwards Lobes Temperature and also the conclusive Ohmical Loss and
Antenna Temperatures together with the G/T_antenna. Strictly as described in the well known Article 'Effective Noise
Temperatures of 4-Yagi-Arrays for 432 MHz EME', Dubus 4/87 by DJ9BV.

Download

You can download the PDF manual from my website as a preview.
Click here to call the Download Mirror on my website

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Note: Noise.exe version 1.0 has an internal flaw handling the comma as decimal separator.
If your computers operating system is set to use the "," as default decimal separator you must change to "."
while using noise.exe.

This occure on German settings and maybe on others too.

Call up your Operating systems 'Regional Settings' and change to English

A screenshot of MS Windows 'regional settings' in Ukrainian language and how to change the decimal separator only.

(tnx to Vladimir, UR5EAZ)

Convergence and Limes,
a simplified mathematical introduction

The strict mathematical definition of convergence is more complex than this Limes or Limit of a function.
But in simple terms we are looking at a sample function f(x), which approaches a Limes, a highest number, towards the value 2.00.
For a certain ε all values of that function are within L = 2 ε from input value S on.
Math.: 'For all x > S the f(x) is within ε of L'.

What does that mean to the antenna designer?

We want 'realistic' antenna simulations. Of such kind, that they can be produced as real antennas
with as close as possible properties to the simulated design. Will the radiation pattern and frequency response
be same as designed? Which way is the model set up the right way and how can that be assured?
The ideal scenario is a design, whose nec geometry could be uses 1:1, maybe with a proven boom correction applied.

What happens when we vary the models segmentation density? Lets look at the YU7EF EF0212 with
wires segmented in 3 different densities:

Frequency response versus segmentation on a DG7YBN 432 MHz YBN 70-5m

We see the point of best Return Loss move by 3.5 MHz while varying the segmentation density and also the Average
Gain approaching a limes. With a segmentation of ~10...15 per wire (= Yagi element) we find a change in the Average Gains
line steepness and a close approximation to the ideal value of 1.000. This may be our L = 2 ε.

For most simple antenna structures, be means of forms or layouts of wires that the used kernel can handle with less divergence
many carefully build and plotted test Yagis with a non metal boom show a relatively good conformity to the simulation
with around 11 segments applied per wire. The desired behaviour shows in the region of change in steepness of the Average Gain
curve line.It must be mentioned that to achieve this a correct length of any applied
symmetrising coax or balun is a necessity.

See here, scroll down to 'Preface ... An example' for a real sample plot
See also here 'How to set up a Measurement Yagi the right way?'
See also here 'The SBC ... a Segmentation Density (Boom) Correction'

For comparing the benchmark parameters of forward gain, F/R, Antenna Temperature and Antenna G/T on an objective base the
Average Gain of the lossless models must be 1.000 or at least 0.998 or so. If one of the design models differs from that
we need to apply a correction on its benchmark parameters. This we call Average Gain Correction. The theory was put up by
Brian V. Cake, KF2YN in Dubus 4/2010.

Most about Convergence problems correction including an online calculator using KF2YN's set of formulas is described on my website
about Average Gain Correction

Numerical Electromagnetics Code (NEC) . Method of Moments
Part III: Users’s Guide, G. J. Burke, A- J. Poggio, 1981, Lawrence Livermore Laboratory
Section II, Structure Modeling Guidelines

1. Wire Modeling

(1)       “The main electrical consideration is segment length Δ relative to the wavelength λ. Generally, Δ should be less than about 0.1 λ at the desired frequency.“

λ = 2.079 m @ 144,200 MHz
0.1 λ =0.1 * 2.079 m = 0.2079 m
A typical 144 MHz Yagi element may have a length of around 0.998 m;

At a segmentation of 10 per wire the resulting segment length is 0.998 m / 10 = 0.0998 m.
That leads to a minimum to chose length factor of 0.2079 m / 0.0998 m = 2.08. In straight words: a segmentation of only 10 segm./wire is better than double of the recommended minimum per manual.

As we continue reading down the manual we find the following:

(2)       “[...] while shorter segments, 0.05 λ or less may be needed in modelling critical regions of an antenna.”

Taking into account 'the minimum to chose length factor' we are still on the side of the recommended solution with just 10 segments per wire. Even if the exciter straight dipole to D1 zone of a Yagi should be considered a critical region. With complexer geometry exiters than a straight dipole this will become a different story.

(3)       “Small values of Δ / a may result in extraneous oscillations in the computed current near free wire ends […]. Extremely short segments, less than about 10E-3 λ should also be avoided […]”.

10E-3 = 0.001 λ 0.001 * 2.079 m = 0.002079 m
2.079 m / 0.002079 m = 1000

segment length = Δ , wire radius = a

(4)       “[…] Δ / a must be greater than about 8 for errors of less than 1%.”



• Here is a sketch I made to illustrate the minimum background

Choosing a common diameter for Yagi elements of 8 mm we arrive at a = 8 / 2 mm = 4 mm
Δ / a = 8 gives us a minimum segment length of ? = 8 * a = 8 * 4 mm = 32 mm.
That equals a maximum segmentation of 998 mm / 32 mm = 31

(5)       “With the extended thin-wire kernel, Δ / a may be as small as 2 for the same accuracy.”

Δ / a = 2 gives us a minimum segment length of ? = 2 * a = 2 * 4 mm = 8 mm.
That equals a maximum segmentation of 998 mm / 8 mm = 124

(6)       “Unless 2 Π a / λ is much less than 1, the validity of these approximations should be considered.”

2 Π a / λ = 2 Π * 4 mm / 2079 mm = 0,0121

On pg. 125 of the manuals we find an example of a Yagi – like structure, take a look at the chosen segmentation:

(7)       “Example of a 12 elem. log peridoc antenna Total 78 segments, No of Seg/wire 9, 9 ,7 ,7 ,7, 7, 7,5 ,5 ,5 ,5 ,5 ”


An other voice

L. B. Cebrik, W4RNL

A Beginners Guide to Modeling With NEC,
Part 4: Loads, transmission lines, tests and limitations,
February 2001 QST:

4nec2 is, speaking in programmer terms 'so open for output', that other programs can read the data sets. Arie Voors even implemented a space for a forseen link to the free gnuplot chart plotting software. So that we do not solely depend on 4nec2's own chart output but may use gnuplots abilites to produce plot charts to our like or needs.

Further we can use this door for data exchange (4nec2 plot folder & Plot.txt file) to read data into a table calculation software for whatever data display, analysis or processing

Wikipedia abt. gnuplot
"gnuplot is a command-line program that can generate two- and three-dimensional plots of functions, data, and data fits"

Link to the gnuplot website

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Based on the instructions for using the '4NEC2_PLOT.xls' by Vladimir, UR5EAZ, I have written a PDF introduction, how to install gnuplot, register it in 4nec2 and produce plot data sets for the above MS Excel application.

Download the 'Extended_Output_from_4nec2_with_GNUplot.pdf'

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An application for analysing and comparing antenna key parameters, the '4NEC2_PLOT.xls' by UR5EAZ.

• Power Gain
• Q-factor (based on the formulars that YU1AW uses)
• Antenna Absolute Impedance
• Mismatch Loss to given Z
• Return Loss
• Antenna Efficiency

Download UR5EAZ's MS Excel '4NEC2_PLOT.xls'

MMANA plots data, which are to be displayed on internal charts into a 'plot' folder so that other programs can read the data sets.

We can use this door for data exchange and read data into a table calculation software for whatever data display, analysis or processing

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Vladimir, UR5EAZ has written instructions for using the 'MMANA_PLOT.xls' MS Excel application, also produced by him .

"Отличительные особенности: расширенный набор анализируемых параметров программных моделей антенн, возможность одновременного анализа двух моделей, упрощенная процедура формирования загружаемых файлов"

Download the document 'MMANA_Plot_v2'.pdf' in Russian Language

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An application for analysing and comparing antenna key parameters, the 'MMANA_PLOT_v2.xls' by UR5EAZ.

• Power Gain
• Q-factor (based on the formulars that YU1AW uses)
• Antenna Absolute Impedance
• Mismatch Loss to given Z
• Return Loss
• Antenna Efficiency

Download UR5EAZ's MS Excel 'MMANA_PLOT_v2.xls' including 2 examples as zipped file