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Measuring 6dB bandwidth

Forums › General Discussions › Measuring 6dB bandwidth

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  • #50208
    cyounkins
    Participant

    For FCC part 15.247, one measurement is 6dB bandwidth. To measure that, I figured it would go to “Occupied bandwidth” -> “% power” and set that to 25% (for 6dB), thinking this was percentage of max power. Well, it won’t let that number go below 70%. Am I missing something? Thanks for any help.

    #50241
    AndrewAndrew
    Moderator

    Hello Cyounkins,

    I apologize, this appears to be a limitation that was arbitrarily set. If you email me I can send you a version of the software which has this limitation removed. Email me at aj@signalhound.com.

    Make sure the latest version is installed (3.0.11) and I will send you a new file for the fix. Let me know if you install the 32-bit or 64-bit version.

    Regards,
    A.J.

    #50348
    cyounkins
    Participant

    Andrew,

    Thank you, but I’m not sure “occupied bandwidth” does what I want it to anyway. The markers at 70% power are *higher* on the waveform than at 90%. Put another way, the occupied bandwidth increases when going from 70% to 90%. If this is percent of max power, the bandwidth should increase as the percentage decreases.

    See screenshots here: https://imgur.com/a1JkgaE,fawq6si

    Can you explain?

    Craig

    #50376
    Justin CrooksJustin Crooks
    Moderator

    For 6 dB bandwidth test, I believe the test is marker peak, then marker to the first point (left-to-right) less than 6 dB below peak, then delta, then last point (right-to-left) less than 6 dB below peak. You may wish to verify this, but I believe this is the 6 dB test.

    #50377
    Justin CrooksJustin Crooks
    Moderator

    Another thing to note: For accurate power measurements, you need to keep the total power into the BB60C below +10 dBm. Your picture showed over +16 dBm. You will want to use a 10 or 20 dB pad for accurate measurements.

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