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Microwave Transmission

Viewing 15 posts - 46 through 60 (of 114 total)
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  • #38358 Reply
    AbdulHaq
    Guest

    I found the following:

    Why 48V voltage is used in telephone systems ?

    The -48V voltage was selected because it was enough to get through kilometers of thin telephone wire and still low enough to be safe (electrical safety regulations in many countries consider DC voltages lower than 50V to be safe low voltage circuits). 48V voltage is also easy to generate from normal lead acid batteries (4 x 12V car battery in series). Batteries are needed in telephone central to make sure that it operates also when mains voltage is cut and they also give very stable output voltage which is needed for reliable operation of all the circuit in the central office. Typically the CO actually runs off of the battery chargers with the batteries in parallel getting a floating charge.

    The line feeding voltage was selected to be negative to make the electrochemical reactions on the wet telephone wiring to be less harmful. When the wires are at negative potential compared to the ground the metal ions go form the ground to the wire instead of the situation where positive voltage would cause metal from the wire to leave which causes quick corrosion.

    #38359 Reply
    G.O.Otieno
    Guest

    What is the differnece between PDH and SDH microwave?

    #38360 Reply
    Shamsul Haque Rubel
    Guest

    We use (8,13,15,23)GHz ODU at vertical & Horizontal Polarization.But what factors depend on design Vertical & Horizontal Polarization on those above frequency.

    #38361 Reply
    Mahak
    Guest

    can any body tell me what is LOG PERIODIC ANTENNAE?

    Egerly waiting for reply.

    Thanks and regards,

    Mahak

    #38362 Reply
    Amit
    Guest

    Hi all ,
    Can any body tell what measures that can be taken to minimise multipath fading when there is no possibilities for space diversity and there is no water body in the
    profile?

    #38363 Reply
    Shamsul Haque Rubel
    Guest

    During the Transmission planning a planner use vertical or horizontal polarization.When we’ll use vertical & Horizontal polarization.Please give me the technical answer.

    #38364 Reply
    Vishwajeet Brijesh
    Guest

    Q.Why polarization is needed in the GSM antenna? What would happen if there were no electrical and mechanical polarization?

    A.To avoid space diversity,Now a days crosspolarised(90* pol. difference b/w TX & RX) GSM antennas are used which can simultaeously work as a TX and RX both,without interference.

    #38365 Reply
    Hamad
    Guest

    why bit error rate has a default value of 10e-6?

    #38366 Reply
    Harpal Sinh Gohil
    Guest

    How circular polarizaion of EM is achieved? Can vertically or horizontally polarized antenna receive circularly polarized waves?

    #38367 Reply
    Anila
    Guest

    Reply to :
    Can any body tell what measures that can be taken to minimise multipath fading when there is no possibilities for space diversity and there is no water body in the
    profile?

    Methods to mitigate multipath fading:-
    1) Strong coding(convolutional or turbo) and interleaving bit errors at the receiver
    2) RAKE RECEIVERS – Most important – to combine energy of most significant multipath components
    3) Inner loop power control

    All this is reference to CDMA/WCDMA

    #38368 Reply
    Hamad
    Guest

    How aperture of MW antenna is related to HOPE distance.

    #38369 Reply
    Shamsul Haque Rubel
    Guest

    Hi,
    sorry to say you are not sending mail my questions answer.you’ve sent mail but that was not my question answer.pls send appropriate answer.

    #38370 Reply
    luka
    Guest

    basic difference between sdh and pdh

    #38371 Reply
    Pix
    Guest

    “SDH differs from PDH in that the exact rates that are used to transport the data are tightly synchronized across the entire network, made possible by atomic clocks. This synchronization system allows entire inter-country networks to operate synchronously, greatly reducing the amount of buffering required between each element in the network.”

    SDH = SONET
    http://en.wikipedia.org/wiki/Synchronous_optical_networking#External_links

    PDH
    http://en.wikipedia.org/wiki/PDH

    Overview (a bit old…)
    http://www.gare.co.uk/technology_watch/sdh.htm

    #38372 Reply
    Avinash Kumar
    Guest

    Rubel

    Regarding the Negative voltage being suplued to BTS particularly in Ericsson BTS. The reason is

    1: This prevents corroson.
    2: This protects BTS during Lightining.
    3 and the main reason, the Noise generally runs to + terminal of the Battery so we use -ve terminal in order to increase the speech level quality.

Viewing 15 posts - 46 through 60 (of 114 total)
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