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This is part 38 of the LoRa/LoRaWAN tutorial.
In this video series different topics will be explained which will help you to understand LoRa/LoRaWAN.
It is recommended to watch each video sequentially as I may refer to certain LoRa/LoRaWAN topics explained earlier.
In this tutorial I will explain what a NEC antenna modelling software is and how to use the 4NEC2 antenna modelling software.
On Internet and YouTube you can find tutorials how to build certain antennas.
But often I wonder what is the performance of these antennas?
What if I use a slightly different wire diameter or slightly change the length of a particular wire?
Will these changes impact the antenna performance significantly of not at all?
Using an antenna modelling software can help you to answer these questions without having to build the actual antenna right away.
NEC (Numerical Electromagnetics Code) is a popular antenna modelling system for wire and surface antennas and simulates the electromagnetic response of antennas and metal structures.
The accuracy of the calculation depends on how well you model the antenna and the information you provide with regard to the ground and wire conductivity.
But be aware, in the real world using the actual antenna, the result will be slightly different compared to the simulation.
This is caused by reflections, weather conditions, where the antenna is mounted etc.
Here are a few NEC antenna modelling software:
EZNEC
Available for Windows.
It has a free and a paid version.
The free version has a 20 segments limit.
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4NEC2
Available for Windows and its free.
This tool has many options.
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cocoaNEC
Available for MAC OSX and its free.
This tool has limited options.
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The previous mentioned 3 antenna modelling software uses the NEC-2 (Numerical Electromagnetics Code) engine which does all the calculations.
NEC was developed by the Lawrence Livermore National Laboratory in the 1970s and is an antenna modelling system for wire and surface antennas.
More information about NEC-2: [ Ссылка ]
The NEC2 documentation is composed of three sections:
Part I: NEC Program Description - Theory
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Part II: NEC Program Description - Code
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Part III: NEC User's Guide
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NEC2 quick reference:
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The length of each segment must be between 5% and 10% of the wavelength.
If the ratio of segment length to wire radius is greater than 8 the NEC engine simulates the current flow in the wire as a very thin current thread.
The NEC engine uses the default "Thin Wire Kernel" (Do not use EK card)
If the ratio is between 2 and 8 the NEC engine should simulate the current to be evenly distributed on the circumference of the wire for a more accurate result.
In this situation you should use the EK card (Extended Thin Wire Kernel).
Never make the ratio go below 2.
4NEC2 software allows inline comments (single quotes) and SYmbol (SY) cards but these are 4NEC2 specific and is NOT part of the NEC2 specification.
Other software such as cocoaNEC will not run when they encounter SY cards.
This card deck can not be run in cocoaNEC because it uses SY cards and inline commands:
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You can use arithmetic operators, trigonometric functions, mathematical functions and predefined identifiers in the Symbol cards.
Do not cross wires.
Do not model elements below the ground (z=0).
cocoaNEC has several limitations which other antenna modelling software does not have.
For example: You can not model helixes in the spreadsheet, and helixes are not displayed in the 3D model.
It is important to see all your antenna elements in 3D to verify if your antenna is correctly modelled.
In cocoaNEC and 4NEC2 wire radius can be entered in American Wire Gauge format.
For example: #12
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More information about 4NEC2:
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Check out all my other LoRa/LoRaWAN tutorial videos:
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Subscribe to my YouTube channel:
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The presentation used in this video tutorial can be found at:
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#mobilefish #lora #lorawan
