Why are high frequencies bands chosen in satellite communication?

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Discussion Overview

The discussion revolves around the reasons for choosing high frequency bands in satellite communication, exploring aspects such as bandwidth, signal degradation, and the impact of atmospheric conditions. Participants examine both theoretical and practical implications of using these frequencies in various applications, including military and non-military contexts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Jose questions why high frequency bands (> 30 GHz) are used despite their susceptibility to signal degradation from atmospheric conditions like rain fade.
  • One participant suggests that high frequencies have less overall loss and can be focused more effectively, which is beneficial for targeted communications.
  • Another participant notes that while higher frequencies can be attenuated quickly, this can be mitigated by using sensitive and powerful receiver and transmitter components.
  • Dave introduces the idea that the 8-15 GHz frequency range is advantageous because it is less affected by ionospheric reflection compared to lower frequencies, allowing for better penetration of the ionosphere.
  • Jose raises a concern about the relevance of security in non-military satellite communications that cover large areas, questioning the applicability of focusing signals for single receivers.
  • RUber agrees that shorter wavelength transmissions can be more focused but clarifies that this is not a requirement for all satellite communications.
  • Another participant emphasizes that geostationary satellites have specific footprints for communications, indicating that coverage is planned for various regions.

Areas of Agreement / Disagreement

Participants express a range of views on the advantages and disadvantages of high frequency bands in satellite communication. There is no consensus on the necessity of focusing signals for all types of satellites, and the discussion remains unresolved regarding the implications of security concerns in non-military contexts.

Contextual Notes

Some participants mention specific frequency ranges and their characteristics, but the discussion does not resolve the complexities of signal degradation, bandwidth capabilities, or the trade-offs involved in using different frequency bands.

curiousman
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Hi all,

I'm an student of Physics so apologies if I'm just some silly questions here.

The higher frequency bands typically give access to wider bandwidths (e.g wifi). Considering that higher frequencies bands (> 30 Ghz) are more susceptible to signal degradation due to ‘rain fade’ (atmospheric rain, snow or ice). Why are they made in order to emit high frequencies? Is information lose once it pass the atmosphere through?

Thanks in advance,
Jose
 
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One benefit of high frequencies is that they tend to have less loss overall and are easier to focus at a single target. Think of something really high frequency, like light. You can direct a focused beam of light pretty far without having too much loss from the atmosphere. Lower frequencies have greater spread, and so require much more energy to retain a strong enough signal at the destination...also security can become a concern if you are transmitting information intended for a single receiver.
 
Since satellites generally are data receieving and transmitting devices, a high band width data capacity is very much an advantage.
It's true that higher frequencies can be attenuated more quickly by rain for example, but that is easily compensated for by making the receiver and transmitter components sufficiently sensitive/powerful for whatever is the the job of the satellite.
 
Thanks guys. Clear enough
 
Rodos said:
Thanks guys. Clear enough
both are good answers,
but there is another serious consideration why the 8 - 15GHz is used for satellite and distant space probe comms that wasn't mentioned

that freq range isn't subject to ionospheric reflection that much lower HF, VHF and UHF freq's are ... that is the microwave freqs penetrate the ionosphere more easily
(and apart from the fact that range of bands is already in full use, it doesn't have the freq bandwidth capabilities
that are available much further up the spectrum

Dave
 
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Thank you all!

I was thinking about your answers and I´m still wandering that if non-militar Satellites use to spread the signal in a great area (TV, Internet, Sat Phone,etc).. so the RUber´s point "also security can become a concern if you are transmitting information intended for a single receiver" wouldn´t make any sense.
 
RUber is right that it's easier to make a shorter wavelength transmission more focused.
There are both military and non military satellites for which that can be useful.
The signal does not HAVE to be more focused though.
 
Rodos said:
I´m still wandering that if non-militar Satellites use to spread the signal in a great area (TV, Internet, Sat Phone,etc)..

wondering not wandering :wink: 2 very different meanings

The geostationary sat's for communications, TV etc have very specific footprints covering various regions/countries etc ... as an example
see this map ... http://www.satbeams.com/footprints?beam=5548
 

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