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  • Air Coupling

    Could it be reduced or prevented by covering any transmitter with some sort of "box"?

    J.C.

  • #2
    Re: Air Coupling



    wtf is your question

    rick.
    phoebe it is

    Comment


    • #3
      Re: Air Coupling

      Originally posted by PLUMBER RICK View Post


      wtf is your question

      rick.
      I DO appreciate your reading my question and willingness to help.

      But that response did make me laugh.

      Are you just messing with me?

      J.C.

      Comment


      • #4
        Re: Air Coupling

        Originally posted by JCsPlumbing View Post
        Could it be reduced or prevented by covering any transmitter with some sort of "box"?

        J.C.
        ???

        Comment


        • #5
          Re: Air Coupling

          Are you asking about capacitive coupling between a
          locater transmitter and nearby commodities such as
          pipes, wires, or cables which are not intended to be
          included in the scan?

          I think what Rick is trying to say is (most eloquently
          I might add) "we need more information".
          ---------------
          Light is faster than sound. That's why some people seem really bright until you hear them speak.
          ---------------
          “If I had my life to live over again, I'd be a plumber.” - Albert Einstein
          ---------
          "Its a table saw.... Do you know where your fingers are?"
          ---------
          sigpic http://www.helmetstohardhats.com/

          Comment


          • #6
            Re: Air Coupling




            I'm with Rick.

            Mark
            "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

            I never lost a cent on the jobs I didn't get!

            Comment


            • #7
              Re: Air Coupling

              Sorry guys. I just usually assume I need to learn more than anyone in the room.

              A transmitter can be used to locate with it's internal frequencies. No connection or inductive clamp.

              Not sure of the exact term but kind of "passive-inductive" locating. Or "drop boxing".

              Air coupling can occur with the transmitter through the air rather than on the utility giving you a false or erratic reading as I understand it.

              Just wondering if covering the transmitter would eliminate this.

              J.C.

              Comment


              • #8
                Re: Air Coupling

                That is a question for a rep indeed! I wish i had the answer!

                Comment


                • #9
                  Re: Air Coupling

                  Air Coupling

                  Air-coupling occurs when the transmitter’s signal travels through open air and is received directly by the receiver. This causes the receiver to sense the signal from the transmitter when what you want is the receiver to sense the signal from the utility line so you can trace it. When you’re close to the transmitter, this direct signal is much stronger than the signal coming from the utility you’re trying to locate and it may add confusion.



                  Air coupling distance can vary over a wide range and you must always carefully confirm that a real utility is detected and that an accurate depth measurement is being made. The air coupling distance can be large, greater than 70 feet (20m) if the induced utility is deep and poorly grounded at both ends. It can be short, perhaps 15 ft (5m) if the induced utility is very shallow and well grounded. Always confirm that air coupling does not distort your readings. Air coupling varies continuously and is not simply an off and on distortion. As you move away from the transmitter the distortion caused by air coupling continues to reduce until the signal from the induced utility dominates and air coupling effects become small.


                  To test for air-coupling using Multi Directional Antennas, tilt the locator about 45° toward the transmitter, with the lower antenna of the locator touching the ground. Then tilt it about 45° away from the transmitter. Observe the depth reading. If it changes significantly, air-coupling is occurring.


                  Another method to test for air-coupling is to stand in the area you want to locate and notice the indicated depth measurement on the locator with the lower antenna on the ground. Then, raise the locator vertically, about 18 inches (45 cm) and observe the change in depth indication. If the locator is reading on the conductor only, the depth will increase accordingly; if it is reading on the transmitter’s field (air-coupling) it will not change by 18 inches, but may change disproportionately.


                  Locator 1 is too close to the conductor and is receiving signal directly from the transmitter through the air, while locator 2 is receiving more or all of the signal from the target utility

                  FROM:

                  http://www.ridgid.com/Tools/Inductio...ling/index.htm

                  Comment


                  • #10
                    Re: Air Coupling

                    If your 'covering' was something that would shield RF yes it would attenuate the signal received at the locator directly through the air I think. Would have to be metal and be RF tight meaning no radio signal could leak out. You might experiment by covering it with a metal bucket and also try grounding the bucket with a jumper wire.



                    Originally posted by JCsPlumbing View Post
                    Sorry guys. I just usually assume I need to learn more than anyone in the room.

                    A transmitter can be used to locate with it's internal frequencies. No connection or inductive clamp.

                    Not sure of the exact term but kind of "passive-inductive" locating. Or "drop boxing".

                    Air coupling can occur with the transmitter through the air rather than on the utility giving you a false or erratic reading as I understand it.

                    Just wondering if covering the transmitter would eliminate this.

                    J.C.
                    ---------------
                    Light is faster than sound. That's why some people seem really bright until you hear them speak.
                    ---------------
                    “If I had my life to live over again, I'd be a plumber.” - Albert Einstein
                    ---------
                    "Its a table saw.... Do you know where your fingers are?"
                    ---------
                    sigpic http://www.helmetstohardhats.com/

                    Comment


                    • #11
                      Re: Air Coupling

                      Sorry I guess I am not use to plumber shorthand. The best way to avoid air-coupling is to move your transmitter further away. Your idea with isolating the transmitter might work but I don't know what you would use or how well it would work.

                      Mark
                      "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                      I never lost a cent on the jobs I didn't get!

                      Comment


                      • #12
                        Re: Air Coupling

                        http://en.wikipedia.org/wiki/Faraday_shield
                        ---------------
                        Light is faster than sound. That's why some people seem really bright until you hear them speak.
                        ---------------
                        “If I had my life to live over again, I'd be a plumber.” - Albert Einstein
                        ---------
                        "Its a table saw.... Do you know where your fingers are?"
                        ---------
                        sigpic http://www.helmetstohardhats.com/

                        Comment

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