If you like this video and want to support me, go this page for my donation Paypal or crypto addresses:
[ Ссылка ]
This is part 37 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 balanced and unbalanced feed lines are,
What balanced and unbalanced antennas are,
And what the purpose is of a balun.
Feed lines can be divided into balanced and unbalanced feed lines.
A balanced feed line consists of two conductors of the same type.
Current flows in opposite direction.
The generated electromagnetic fields cancels each other out.
A ladder line (twin lead with rectangular openings) is a balanced feed line.
Ladder lines are used for example in amateur radio systems.
An unbalanced feed line has a single conductor.
A coax cable is an unbalanced feed line.
In LoRa systems coax cables are used.
Antennas can be divided into balanced and unbalanced antennas.
In general (in most but not all cases) a balanced antenna has more than one element which are fed and are of equal length.
An unbalanced antenna has only one element which is fed.
If a coax cable is used to feed a balanced antenna, a small amount of current (lets call it stray current) can flow back along the metallic shield of the coax cable.
The metallic shield acts like an antenna generating RF interference impacting the antenna itself as well as electrical systems nearby.
A balun prevents stray current to flow back along the metallic shield of the coax cable.
A balun can also have another function.
It can be used to connect lines of different impedance.
It can fix the impedance mismatch between feed line and antenna feed point.
For example a dipole antenna feed point has an impedance of 75Ω and the coax cable has an impedance of 50Ω.
By using a 1.5:1 balun the impedance is converted from 50Ω to 75Ω (1.5 x 50Ω = 75Ω)
A dipole antenna can operate satisfactorily without the use of a balun.
It has no significant effect on the VSWR but there may be a slight increase risk of interference if one is not used.
In portable, handheld and IoT applications, tiny low power UHF baluns can be used.
UHF means Ultra High Frequency.
UHF frequency range is: 300 MHz - 3 GHz
Examples how to use a balun:
[ Ссылка ]
[ Ссылка ]
A balun is a balanced to unbalanced transformer.
It takes the unbalanced input from a coax cable and provides a balanced output for the balanced antenna.
A balun is not needed when:
- balanced feed line feeds a balanced antenna
- unbalanced feed line feeds an unbalanced antenna
A balun should be used when:
- balanced feed line feeds an unbalanced antenna
- unbalanced feed line feeds an balanced antenna
In the previous slides I have shown some of my self build antennas.
I have not used baluns.
An antenna can operate satisfactorily without the use of a balun but there may be a slight increased risk of interference if one is not used.
My self build antennas are not properly constructed and the antenna performance can be improved by using better materials, parts or another way of construction.
The antennas in this LoRa/LoRaWAN tutorial series are mainly intended for educational purpose.
My antennas are constructed in such a way so it can be easily disassembled and its parts can be re-used in other antenna projects.
This means the antenna performance will not be great.
Check out all my other LoRa/LoRaWAN tutorial videos:
[ Ссылка ]
Subscribe to my YouTube channel:
[ Ссылка ]
The presentation used in this video tutorial can be found at:
[ Ссылка ]
#mobilefish #lora #lorawan
