What are the fields of an electromagnetic wave?
Antennas create an electric field which has an associated magnetic field.
When radio signals travel at specified radio frequencies, they are called frequency bands.
How are frequency bands used?
Countries, standards and also companies (which e.g. produce sensors) can have their own frequency bands. Though there are also unlicensed bands which can be used by everyone.
Bands are divided into channels of which some are used for advertising (handshakes, etc.) and some for data. Multiple bands are refered to as a spectrum.
Radio channels are extremely random, very localized, difficult to analyze and fluctuate. This is partially due to the Multipath Effect.
Which Multipath Effects can occure in radio signal propagation?
Reflection
Refraction
Shadowing
Scattering
Diffraction
Representations:
Multipath effects can lead to Inter Symbol Interferences (ISI).
What are they?
The main signal energy travels the direct way and arrives at the gateway (GW) after suffering free space path loss.
Because signals are not (everytime) directed, they can e. g. reflect from a building to arrive delayed and distorted at the GW.
This leads to a similar effect as noise.
Which radio propagation ranges exist?
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