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Directive RF through 2ft concrete to pickup?

Discussion in 'Radio and Wireless' started by FuZZ1L0G1C, Apr 30, 2019.

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  1. FuZZ1L0G1C


    Mar 25, 2014
    Want to follow and trace a paint-peeling leak mark in basement garage to the floor above this plinth, which is a passage near the bathroom.
    I suspect a galvanized steel (or copper) pipe has rotted from old age, and is buried somewhere under the floor.
    I want to build a coil or other antenna connected to an oscillator (modulated or tone), to penentrate about 2ft of concrete plinth.
    The oscillator / transmitting circuitry is no problem - I have books with dozens of osc/rf circuits.
    What I would like to find out is best frequency group (ELF / LF / MF ...) and which antenna or coil design would be directive at this short range (2ft>> TX-RX), allowing slight "spread" for detecting transmitter if off center.
    One person holds transmitter on mark at bottom, while other slowly sweeps across the floor in passage.
    When signal is loudest, floor is marked.
    Repeats process for rest of paint-mark (1 - 1.5 poslocator.png m).
    Avoids plumber having to lift all tiles and chop entire floor up to search bad spot.
    Would planar be the best send/search coil?
    As reading up on these animals, they apparently transmit perpendicular to the coil plane.
    As higher RF is attenuated by solid matter, should I go LF?
    I'm thinking maybe even 30-50Khz to create a pulsed tone.
    My books have various transmitter circuits incl LW/MW/SW/HF/VHF.
    What about 27MHz?
    ....Or is my logic too fuzzy?
    Regards, Fuzzy "Clive " Logic.
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Look up "stud finder" in your favorite search engine. Heaps of circuits will turn up.
    In my experience locating hidden pipes etc. is notoriously difficult with inexpensive equipment. In your case the concrete is most likely reinforced and the steel bars of the reinforcement will give you lots of false signals :(

    Anyway, once you've located the pipe, how will you locate the leak?
    FuZZ1L0G1C likes this.
  3. FuZZ1L0G1C


    Mar 25, 2014
    The (cold) water drips through a crack in the plinth underside, yellowing and peeling the paint.
    The idea I had is to use a "signal proximity" method rather than metal detector.
    I have a small home-made FM BCB mike / transmitter as well, so plan to also try this, fed by modulated audio signal source.
    .... .... .... .... .... .... .... .... ....
  4. duke37


    Jan 9, 2011
    I have used a CMOS 4093 as modulated transmitter, built into a 35mm film cassette, connected to one end of a wire and used a small medium wave radio as the sensor. The depth was about 300mm. I have also chased wires inside the house and found a connecting box which had badly overheated.
    I recently had a leak in a water pipe outside the house and the water authority tried to trace it and failed. The fault was cured by isolating the pipe and fitting an alternative.
    FuZZ1L0G1C likes this.
  5. FuZZ1L0G1C


    Mar 25, 2014
    Thanks for the replies.
    This is actually for a friend in distress, as their shiny black Merc also gets a white splatter-paint job when parked under their house.
    The plumber told them it will cost about R8000-R10000 to perform a leak test with their fancy equipment.
    I offered to help out with narrowing down the suspect area on the floor above.
    My train of thought being that the oscillator and coil will always come in handy for other purposes, after.
    I used to have a Hellermann-Tyton industrial stud-finder-cum-mains cable detector.
    Looked like a flat yellow saucer with a handle & sensitivity controls.
    Unfortunately it got stolen during a burglary. - Quite expensive, too!! . . $%#@^&!! thugs.
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