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Intercepting satellite communications

Discussion in 'Radio and Communications' started by sram, Apr 28, 2016.

  1. sram

    sram Member

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    Hi to all.

    I was under the impression that satellite communications are harder to intercept/jam because the signal is concentrated and sent like a beam so that it can reach the very far communication satellite (Usually a geostationary satellite that is 36,000 Km away). That's how a dish antenna emits the signal. In order to intercept such a signal, you will have to place your intercepting antenna somewhere along the path the narrow beam is following in its way to reach the satellite.

    If we imagine a normal whip vertical antenna, the signal being emitted will form a donut like shape around the vertical metallic pole--if you will-- and will propagate as if the donut is growing in size. The signal will essentially be everywhere assuming you are within range and the output power used was enough to reach you. That is the radiation pattern of the whip antenna. I was always telling myself it is much easier to intercept LOS communications when compared to satellite communications since their signal follows a narrow street if you will till they reach their destination.

    I was attending a workshop where presentations were given about SATCOM, and I raised the question: Is it right to say that SATCOM are harder to intercept? The answer-to my surprise-was actually it is easier to intercept. Even a hobbyist can do it. When the satellite sends back the signal, it sends it everywhere or more precisely let's just say the signal will just be there if you are inside the spot beam the satellite is creating...

    Now wait, satellite antennas don't have to be dish antennas. They can be many other types of antennas. That's another reason! It can be an antenna that radiates the signal spherically outward. So the signal will just travel everywhere. Part of it will reach the satellite and establish a link, right?

    Can you please shed some light in here? Can we really say that-in general-satellite communications are easier to intercept?

    Thanks
     
  2. nsaspook

    nsaspook Well-Known Member

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    If you mean from a ground station then generally it's harder to intercept the satellite uplink. The satellite downlink intercept ease depends on many factors like type of orbit (polar, geostationary, etc ...) , type of modulation (coherent carrier, spread-spectrum, etc ...) , transponder footprint, etc ... . General use SATCOM/DBS systems are designed to be easy to receive but it's not a requirement for them or terrestrial radio systems.
     
  3. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    It is much harder to fit a large dish on a satellite, so only the ground end tends to use large dishes. That means that the satellite does not transmit a narrow beam; only the ground station does... It will be much harder to intercept the uplink than the downlink.
     
    Last edited: Apr 29, 2016

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