What Type of Signal Do Satellites Use?

Discussion in 'Wireless & RF Design' started by ajm113, Jan 1, 2012.

  1. ajm113

    Thread Starter Member

    Feb 19, 2011
    The world of satellites interest me and after seeing someone make the world smallest satellite just using a a small IC, Small Solar Cells using only one SMT PC Board. This got me wondering what the science is behind data transmitting from a satellites? I kinda want to experiment a little to get a better understanding of the work behind these guys.

    If I'm correct the first satellite ever made was from Russia and it used Radio frequencies, so people with HAM Radios could pick up it's transmitting signal. I'm guesting most satellites still go this route, because of the white noise interference we get from our radios? Correct me if I'm wrong.

    Thanks, Ajm.
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
    We've come a long way since Sputnik. While lower frequencies have been used, most satellite transmissions are at microwave frequencies. These frequencies allow the use of smaller, lighter antennas; punch through the ionospere better and carry more information than lower frequencies. Amateur radio enthusiasts (hams) communicate with AMSAT at 1.2 GHz, often using only a handy talkie and a handheld antenna.

    Senior Member

    Jun 29, 2010
  4. ajm113

    Thread Starter Member

    Feb 19, 2011
    Wow, very interesting stuff! That would explain how the world smallest Satellite was just one IC or "MIC". All of this has gotten me interested in building my own... Well just for fun of course, since I'm a bit broke to launch it into to our orbit for real.

    If I may ask, I know there are students learning how to build satellites at collages, but are there people out there that just design them as a hobby who might share their engineering knowledge?
  5. bertus


    Apr 5, 2008

    Of course, you have a lot of kinds of satelittes.
    There are the communication satellites, for TV broadcasting and telephony.
    There are GPS satelletes for location deternination.
    There are wheater satellites, for measuring and spreading information on the wheater.
    There are deep space satellites, for exploring deep space.

    Here is a page from the EDUCYPEDIA with links on several types:

    Next to all commercial satellites there are also several amatuer sattelites like the oscar series:
    More info on amateur satellites can be found here:

    Last edited: Jan 1, 2012
  6. Blofeld

    Active Member

    Feb 21, 2010
    Even if you could shut down every external source of electronic interference (including satellites), you would still hear some white noise. It is a fundamental property of all electronic components that they generate at least thermal noise and shot noise.

    Now if you forget this type of noise for a moment, and only look at external noise sources, this is a very interesting question: How much do the signals from satellites contribute to this noise ? I don’t claim to be an expert here, but I would just guess that if you are living in a city, the electronic interference from all kinds of electronic devices in the neighborhood is stronger than the interference from the satellite signals. Probably it’s another thing if you are sitting in a very remote area like a research station in Antarctica. Or just in a valley where you have no Line-Of-Sight connection to any other source of electronic interference. Maybe in these cases the noise from the satellite signals is really dominant.
  7. Adjuster

    Well-Known Member

    Dec 26, 2010
    That's an interesting example of coming to a (more or less) correct conclusion from an argument that does not really support it.

    As has been pointed out, there is lots of electrical noise around, both arising within electronic equipment and outside it, the latter including both man made and natural sources. Don't forget lightning, the sun, the stars, and (so they say) even echoes of the formation of the universe. Interference from satellites must be a drop in the bucket - and mostly occurs at frequencies not used for terrestrial broadcasting.

    More to the point, if satellites did not use Radio Frequencies, what could they use? Perhaps it may be worth looking at a definition. http://en.wikipedia.org/wiki/Radio_frequency

    If we say that RF extends up to 300GHz, we see that it includes just about any signal which can be generated electronically - not just the frequencies used by ordinary sound radio. In fact, satellites mainly use higher frequencies than ordinary radio, because some of the the lower frequencies do not penetrate the upper atmosphere so well, and also because more information can be carried on higher frequencies.

    Finally, frequencies are allocated by national and international agreements for use for different purposes, so as to minimise interference. Here is a chart for the USA - if you click on it and get an enlarged version, you will see that satellites use mainly higher frequencies. http://en.wikipedia.org/wiki/File:U...locations_Chart_2011_-_The_Radio_Spectrum.pdf
  8. ceidas


    Dec 26, 2011
    Nice chart! Do we also know what type of modulation is been used in each one of them?