different microwave radios working on same freq & direction

Discussion in 'Wireless & RF Design' started by sathya_j2084, Oct 27, 2009.

  1. sathya_j2084

    Thread Starter New Member

    Oct 27, 2009
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    hello

    how does two microwave links with radios of diifferent vendors (Ericcson and Fujitsu) work along the same direction, same frequency and same polarisation without interfernce?

    thanks
     
  2. davebee

    Well-Known Member

    Oct 22, 2008
    539
    46
    They might be using spread spectrum radios, in which case they don't actually use the same frequency at the same time.

    The spreading function, whatever it may be, makes the instantaneous frequency jump around near the center frequency using a different pattern for different users, so users actually use different frequencies most of the time. Otherwise there would be interference.
     
  3. wr8y

    Active Member

    Sep 16, 2008
    232
    1
    I think davebee is right, however, one other thing - are they on the same frequency EXACTLY or just the same BAND? If they are labeled, say, "21 gHz", that means they are in that band, but not exactly on 21.000000000 gHz.

    We do have a site with several (cant remember now 3 or 4) transceivers all on 5.4 gHz. They are in that BAND, but not exactly on the same frequency at the same time. They do, in fact, all use a form of frequency hopping. We have no idea of knowing what exact frequency they are EVER on.

    This is the unlicesed "U-NII" band. Here is a little about it - sorry it's from WIKIpedia! http://en.wikipedia.org/wiki/U-NII
     
  4. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    They got lucky
     
  5. sathya_j2084

    Thread Starter New Member

    Oct 27, 2009
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    hello

    the two radios are exactly on the same frequency. Should there be patented process for freq hopping for each radio manufactures so that one does not interfere with the other or does schemes like emmision code come into play?
     
  6. wr8y

    Active Member

    Sep 16, 2008
    232
    1
    Ok, so what frequency are they on?

    What type of information is being transported on each one? (I mean, voice, data, video...?)

    What kind of modulation is each using?

    (The answer to YOUR question is likely found in the answers to THESE questions.)
     
  7. sathya_j2084

    Thread Starter New Member

    Oct 27, 2009
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    Are 128 QAM scheme and 128 MLCM scheme the same?
     
  8. wr8y

    Active Member

    Sep 16, 2008
    232
    1
    Those are modulation methods, not frequencies.

    QAM - Quadrature amplitude modulation

    MLCM - Multilevel Coded Modulation

    The "128" is not a frequency, but a modulation designator. The Frequency should be indicated in gHz or mHz.



    Anyway... read up on what I put above, I"m off for three days with my car club! :)

    Bye for now!
     
  9. sathya_j2084

    Thread Starter New Member

    Oct 27, 2009
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    i do understand that QAM and MLCM are modulation schemes.But do they have any significant differences?
     
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