Microwave vs Radiowave communications & analogue and digital

[Saado]

Why are raidowaves used for Wifi and Bluetooth but microwaves for satellite communication among other things. I was under the assumption that radiowaves are used for communication only. What are the factors which play into this decision. Also, is there a link between frequency of a wave and the amount of information it can carry?Also, can electromagnetic waves take the form of analogue signals and how does this work exactly? Creating analogue and digital signals in terms of the electromagnetic wave produced.

 

[jtbell]

Why are raidowaves used for Wifi and Bluetooth but microwaves for satellite communication among other things.

Microwaves have shorter wavelengths so you can make beams that are more directional. You waste less energy in sending a signal to places where the satellite isn't.

Also, can electromagnetic waves take the form of analogue signals and how does this work exactly?

Google for "amplitude modulation" and "frequency modulation."

 

[Saado]

So I take it that energy efficiency is the only reason they're used? I read somewhere (vaguely) about ways that micro and radio interfere with certain things which make it more practical to use microwaves for long distances and radio for short distance communication. Is that right and if so, what are the specifics?

 

[davenn]

Why are raidowaves used for Wifi and Bluetooth but microwaves for satellite communication among other things. I was under the assumption that radiowaves are used for communication only.

firstly ... microwaves ARE radio waves

microwave radio signals are used for space communications
1) for the reason jtbell gave
2) they are less affected by the ionosphere as they pass through to the satellite or other spacecraft
... that is ... lower frequencies ... HF, VHF and UHF signals are more readily reflected off the ionosphere and come back to earth
virtually all the deep space probes to the other planets and beyond all use the 8 to 9 GHz frequency range.
The majority of satellite TV and similar use the 11 - 14 GHz freq range

the lower in freq the worse the effect. which is why lower frequency HF is used for worldwide shortwave communications and
general broadcast stations. They take advantage of those ionospheric reflections

On earth, microwave radio links are used for things like cellular phone tower site to tower site
Links between broadcast radio or television studio and transmitter sites
this is primarily because of 2 reasons
1) again as jtbell's comments about directivity of the signal and 2 when using digital rather than analog,
much more data can be handled at the higher microwave frequencies

personally for my experiments on the microwave bands as an amateur radio operator,
I mainly use analog rather than digital on 1.2, 2.4, 3.4, 5.8, 10 and 24 GHZ bands
the only digital I have played with was some digital TV on 1.2 GHz all the rest has been analog signals either FM or SSB

cheers
Dave