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RF transmitter circuit

Discussion in 'Radio and Wireless' started by freakinshoe69, Sep 24, 2017.

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  1. freakinshoe69

    freakinshoe69

    3
    0
    Sep 20, 2017
    I want to build a bug to that transmits on a frequency that I can pick up on my portable police scanner. Like a baby monitor. Ive google the crap out of it and cant find anything conclusive any and all help would b appreciated. This is for my own house.
     
  2. davenn

    davenn Moderator

    13,901
    1,971
    Sep 5, 2009
    all the common ones transmit in the FM band between 88 and 108 MHz
    there's zillions of ccts on the net for them
     
  3. 73's de Edd

    73's de Edd

    3,224
    1,349
    Aug 21, 2015
    SIR freakinshoe69 . . . . .


    Could we suggest . . . for utter simplicity . . . . . none other than a a baby monitor transmitter . . . . . . .acual DC supply power is usually 9VDC.
    Availability . . . as used item . . from . . .
    Yard sales . . . . Garage sales . . . . Flea markets . . . .Schindlers . . OOOps . . .Craigs list . . .
    Typically 1-5 bux used.

    E -bay
    https://www.ebay.com/sch/Baby-Monitors/20435/i.html?_from=R40&_nkw=used+baby+monitors&_sop=15


    IF you still just INSIST on building GOGGLE UP modulated FM transmitter circuits and . . . . . thatsalookalikea . . ..

    POST GOOGLIFIED:
    https://www.google.co.in/search?tbm=isch&slpassthru=1&q=Modulated Fm Transmitter Circuits
    ( NOTICE
    . . . one circuit per customer . . . . . limit.)

    73's de Edd
     
  4. freakinshoe69

    freakinshoe69

    3
    0
    Sep 20, 2017
    thanx for the help, i am new to this and and didnt know exactly what i needed to google
     
  5. freakinshoe69

    freakinshoe69

    3
    0
    Sep 20, 2017
    i found a lil fm transmitter kit on amazon for $4
     
  6. 73's de Edd

    73's de Edd

    3,224
    1,349
    Aug 21, 2015
    SIr freakinshoe69 . . . . .

    If this is being it . . . .

    https://www.amazon.com/DIY-Wireless...506277963&sr=8-10&keywords=fm+transmitter+kit

    Hmmmmmmmmmmm looks like they are giving you two units . . .

    Looks like its construction and following testing / evaluation will be an initial Baptismal under fire for you on RF oriented electronics..
    The meager 3V power may give 10-15 ft range . . . with you having to try it to exactly see .
    Also the simple circuit will be subject to hand capacitance / handling in a detuning of the operating frequency, so set up the "bug ?" into its fixed hiding place and tune in to its related frequency WHEN distanced away from the unit..

    The length of wire used as the transmit antenna . . .connected onto C7 will have an effect on range . . .initially, watch what info they suggest .
    Since a short 6 inches is inadequate. . .but 25 feet is an INSANELY unrealistic assumption . . . that length would work even BETTER..

    Also the signal propogation at the 108 high end of the FM band is better than the 88 low end, and at that 108MC end . . . a straight vertical wire antenna of ~36 inches length would be in order..

    73's de Edd
     
    Last edited by a moderator: Sep 24, 2017
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