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  1. #1
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    Wideband meter suggestions

    Im looking for a simple yet rather accurate circuit to measure ambient rf power. This circuit should be 100Mhz - 6Ghz. IIRC a precision rf diode fed with just around of potential to overcome its particular semi conducting voltage threshold will output on the order of microwatts if coupled to a wideband arial. Im likely going to build a mini equiangular spiral antenna just because its ideal for such a wide band meter. MY MAIN CONCERN is NOT the arial or the output circuitry (which can be made really fancy with displays and such) rather its the actual acquisition mechanism itself. Perhaps the diode method is faulty and this is why I would like input to a legitimate rf power acquisition method for this wide band meter. All I need is a potential or current to relate to some rf power at some frequency preferably frequency to power stays linear. Please keep any digital circuitry out of your recommendations. Im sure this can be achieved with analog only components.

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  2. #2
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    Re: Wideband meter suggestions

    A transistor/ fet can have its bias adjusted to a
    level so it responds to a very low threshold signal from an antenna. Then amplifies it. This is a step better than the diode detector idea.

    The link below has a gallery of wideband rf detector circuits. An internet search turned up myriad more. I received a simple field strength detector with a kit I purchased, which broadcast mic audio to a nearby fm radio.

    http://www.hobbyprojects.com/F/Field...th_Meters.html



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  3. #3
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    Re: Wideband meter suggestions

    Quote Originally Posted by BradtheRad View Post
    A transistor/ fet can have its bias adjusted to a
    level so it responds to a very low threshold signal from an antenna. Then amplifies it. This is a step better than the diode detector idea.

    The link below has a gallery of wideband rf detector circuits. An internet search turned up myriad more. I received a simple field strength detector with a kit I purchased, which broadcast mic audio to a nearby fm radio.

    http://www.hobbyprojects.com/F/Field...th_Meters.html
    I suppose mosfets are ideal fets for the task. I also assume the least Cgs & Cgd fets are optimal. Pretty much I should use an RF mosfet or are jfets more suited for this task? Since jfets don't have much of a threshold voltage.



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  4. #4
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    Re: Wideband meter suggestions

    What's the intended power range? Do you expect true power reading for multi-frequency and modulated input?

    Usual solutions are thermal and square law diode detectors.



  5. #5
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    Re: Wideband meter suggestions

    Why not use an integrated detector. Examples: ADL5920, ADL5910, ADL5903 or LTC5587



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