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  1. #1
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    coaxial cable impedance

    Hi all,
    I need a coaxial cable with impedance 50 Ohm. After looking at my local electronic store there is only 75 Ohm Coaxial cable. Is there any way to converting 75 Ohm Coaxial Cable into 50 Coaxial Cable ?? perhaps by adding some circuit?? Please help me. Thanks

    Regards,
    Elits

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    50 ohm to 75 ohm converter

    A transformer, minimum loss attenuator, or LC network will work. If you do not know how to design these, you would be better off buying 50 ohm cable via the internet.

    Your application might work with 75 ohm cable.



    •   Alt30th October 2006, 23:38

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  3. #3
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    cable impedance

    Code:
    Impedance matching network usign resistors
    The matching network shown below can be used to match two unequal impedances, provided that Z1 is grater than Z2. 
    
              ____
         ----|____|---+---------
               R1     |        
                     | |        
       Z1            | | R2     Z2
                     |_|        
                      |         
         -------------+----------
    
    The resistor for this circuit can be calxulated using the following equations: 
    
      R1 = Z1 - Z2*R2 / (Z2+R2)
      R2 = Z2 * sqrt(Z1) / (Z1-Z2)
    
    The table below will show some precalculated values for some most common interfacing situations: 
    
      Z1      Z2      R1      R2     Attenuation
     (ohm)   (ohm)   (ohm)   (ohm)   (dB)
    
       75      50     42,3    82,5    5,7
      150      50      121    61,9    9,9
      300      50      274    51,1   13,4
      150      75      110     110    7,6
      300      75      243    82.5   11,4
    Regards,
    IanP



    •   Alt31st October 2006, 01:02

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    75 ohm to 50 ohm balun

    A balun converts between balanced and unbalanced, hence it's name.



    •   Alt31st October 2006, 04:23

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    impedance matching coax

    yeah u r right...



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    50 to 75 ohm converter

    You can convert the 75 Ohm coaxial cable to 50 ohm coaxial cable or vice versa by adding a Balun (Balanced Unbalanced) having impedance =sqaureroot of(75*50)


    Or in other way you can use a transformer or a parallel resistor circuit .



  7. #7
    kyg
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    75 ohm to 50 ohm converter

    may i know what kind of adapter to used to convert coaxial cable impedance from 50ohm to 75 ohm



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    50 ohm to 75 ohm balun

    balun trensfomer or quater wave tranformer transmission line can be used for impedance matching



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    50 to 75 ohm balun

    Elits,
    As IanP stated, a simple Resistor network can be used. However, this method results in power loss. A matching transformer will provide an impedance match with (theoretically) no loss. The turns ratio will be the square root of the impedance ratio. In your case, Sqrt(75/50) = 1.224. Others have mentioned the use of a balun. This would work, but is overly complex. Since both coaxial cables are unbalanced, the balanced - unbalanced feature provides no useful function. You probably won't be able to find a commercially available balun for 75:50 conversion.
    Regards,
    Kral



  10. #10
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    convert 75 ohm to 50 ohm

    See if you can find a 50 ohm to 75 ohm matching transformer (I think it's quite common and avaliable in hardware stores).

    Regards



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    75 to 50 ohm balun

    I guess a quarter wave transformer will do the job....the impedance of the tansformer line would be sqrt(75*50)



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    Re: How to Converting coaxial cable Impedance from 75 to 50

    Hi:
    In TEST equipment if the outputs are set to 50ohm just put a 25 Ohm resistor in series and calculate the insertion loss. (Method recommended by Marconi Instruments)

    Regards



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