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Magnetic Loops for Mobile Phones

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  • Magnetic Loops for Mobile Phones

    I do not know if anyone has thought of this before. But it seems very few makers of mobile phones have the decency to include magnetic induction loops inside, similar to some land line phones. These enable modern hearing aides to pick up audio nearby. Likewise very few TVs, MP3 players have loops installed.

    However the small LW coils on small pieces of ferrite rods for radios are capable of transmitting the audio signals picked up by a hearing aid with a loop. The coils just need connected to the low impedance earphone socket of a mobile etc, and placed within an inch or so of the hearing aid. Alternatively you can wind a coil of some 100 turns of more of very fine enamelled wire. The piece of rod can to be snapped off the rod, need only be about 1 inch or less long. Scoring around the rod with a saw or file may help it break in the right place You may need to experiment which direction the tiny rod needs to be near the hearing aid. Two rods could be attached to a headband for a stereo plug

    There are of course many other very expensive ways of transmitting the audio signals, such as powerful amplifier employing a mic, even a loop placed around the neck, or complicated wire loops installed all around rooms.


  • #2
    Re: Magnetic Loops for Mobile Phones

    Just a further update on these experiments. If you are winding your own coils it is actually best to wind at least 200 turns. The ferrite rod with or without coils can still be bought on Ebay, and even suitable tiny rods of about 1 inch long.

    Since the output impedance of an earphone of speaker socket is low around 8 ohms it should not be necessary use screened wire, especially if using a long wire connected to a TV or HI-FI. My friend says it makes no difference which way the rod points near his hearing aids.