oscope bandwidth

Discussion in 'General Electronics Chat' started by concievo, Nov 13, 2010.

  1. concievo

    Thread Starter New Member

    Nov 13, 2010
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    In order to measure transceiver circuits up to 50MHz , what is the minium bandwidth of an oscope needed.
    I have read that you should get one that has a BW of five times the frequency of the circuit under test. If that is so then it's way out of my budget envelope,but a 50 MHz one is not.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    You have read well. To be able to view a signal on the scope accurately you need a scope with at least 5 times the measured signal bandwidth. If you use a 50MHz scope to measure a 50MHz signal, you will see its amplitude/sqrt(2) on the scope and it will be phase shifted too.
     
  3. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    If the oscilloscope has a bandwidth of 50 Mhz, they mean that it is the - 3 dB point of the scope.
    Read the XYZ of oscilloscopes for more info.

    Bertus
     
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  4. Rbeckett

    Member

    Sep 3, 2010
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    Bertus, your depth of knowledge and ability to link valuable info never ceases to amaze me. I can only aspire to one day have the depth you exhibit on a daily basis. Thanks!!!
    Bob
     
  5. concievo

    Thread Starter New Member

    Nov 13, 2010
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    0
    Thanks for the info gentlemen, but alas I am still confused (an old dog finding it hard to learn new tricks).

    I am finding differing opinions on the subject i.e.-

    5-10 times the f under test for Digital circuits.
    2-3 times for Analog.

    As I have bought a Rigol DS1052E (50 MHz) for $400 new, and I would dearly love it if 2 times for Analog was correct. I will be building QRP gear up to 17M from Ham produced kits. Iam a new Ham,but not entirely new to electronics -serving in the USAF as a Radio/and Nav Aids Tech way back when solid state was just taking over (57-66).

    The above scope can be hacked to 100 MHz if you get the one with the old Firmware,saving $300. See EVV blog site episode #70. Please delete that if not acceptable.
     
  6. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Digital signals need more bandwidth in order to capture their fast rising/falling edges accurately. Analog signals have slower rising/falling times and thus they need less bandwidth to be captured with acceptable accuracy.
     
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