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Simple signal generator question

Discussion in 'Electronic Design' started by BenL, Jun 20, 2007.

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  1. BenL

    BenL Guest

    Hi all. I have an old signal generator (HP 8656B) that only goes down
    to -127dBm. However, I would like to do measurements at lower levels
    than this, down to maybe -137dBm. Can I just connect a 10dB
    attentuator to the output of the signal generator and then subtract
    from the output power shown on the display? Seems like I can, but
    maybe its not that easy.

  2. Chuck

    Chuck Guest

    That depends a lot on the signal
    generator itself and the integrity of
    its case and shielding. You will
    definitely get additional attenuation,
    and the attenuator steps on the signal
    generator should remain accurate. Your
    additional attenuation may be slightly
    less than 10dB, however, due to leakage.

    I guess the real question is how
    accurately must you know the absolute
    output level? For that matter, how
    accurate is the generator output level
    now at -127dBm?

  3. It is that easy if the load you are driving approximates 50 ohms resistive.

  4. Charles

    Charles Guest

    That unit goes up to 2 GHz (according to my Internet search). At higher
    frequencies, shielding becomes tricky. You can add attenuation but might
    face leakage paths.
  5. neon


    Oct 21, 2006
    at that level -127 db or 137db the qustion is how can you measure i. a scope will help but te loading well good luck.
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