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20 dB Attenuator for GSM Field Meter

Discussion in 'Electronic Design' started by [email protected], Apr 3, 2013.

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  1. Guest

    I have a digital field strength meter covering the 800MHz to 2.5GHz
    range To it is connected, via SMA cable, a log periodic antenna. The
    available reading only goes to 1999 uW/m2. I would like to place a
    20dB attentuator in-line with the antenna to increase this by a factor
    of 100.

    Can anyone please suggest what circuit or components to use? Is
    something like this all I need?

    Can I assume the meter's input impedance is 50 Ohms?

    Richard Jones
  2. Jasen Betts

    Jasen Betts Guest

    If only it was that simple! at 800 to 2.5Ghz layout is going to be critical if
    you want a flat response over that range.

    At the first online supplier I checked 3GHz attenuators seem to start at
    around $40 for upto 10dB, 20dB is twice as much.
    If it's not it'll probably written somewhere near the input
    TV uses 75 ohms, but most other things are 50 ohms.
  3. Guest

    How is the actual measurement instrument protected against direct
    radiation penetration ?

    Sure, you can insert various attenuators along the line, but if the
    signal source will penetrate directly in to the equipment from the
    air, you are in trouble.
  4. Fred Abse

    Fred Abse Guest

    SMA are 50 ohms, hence yes.

    Use a Pi-section attenuator, theoretical values are 61.11 ohms, 247.5
    ohms, 61.11 ohms.

    Good luck with getting it to stay resistive up to 2.5GHz.
  5. Am 04.04.2013 12:29, schrieb Jasen Betts:


    Minicircuits DC-6GHz SMA Attenuatos, regardless of the AttenFactor
    are around 12$/Piece..!

    have a look:




    A really nice one!
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