Need Help! Antenna location on this board

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Discussion in 'The Projects Forum' started by Etronic, Jul 15, 2013.

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  1. Jul 15, 2013 #1
    Etronic

    Thread Starter Active Member

    Oct 7, 2011
    127
    2
    Hi all.

    Can someone tell me where the antenna would be connected to.:confused:

    And where i could add an extra wire lead to the trace.

    To get a longer range for this transmitter.

    I've gotten no information from the manufacturer on this.

    I need to know where would the circuit board antenna
    be located on this board.
    There's a TX chip on the side of the battery hold.

    Photo's Enclosed.
     
    Last edited: Jul 15, 2013
    #1 Reply
  2. Jul 15, 2013 #2
    LDC3

    Active Member

    Apr 27, 2013
    920
    161
    I am guessing, but I would say that the loop on the board is your antenna. Unfortunately, unless you have the correct length of wire to extend the antenna, you end up losing signal strength since the antenna is no longer tuned to the frequency.
     
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  3. Jul 16, 2013 #3
    Etronic

    Thread Starter Active Member

    Oct 7, 2011
    127
    2
    LDC3

    Which loop are you guessing at. Are talking about the round circle.If not where.Please point to it.

    And the length of the wire would be the length of the loop.I'm assuming.


    Anybody else on this site have any idea where the correct spot the antenna is
     
    Last edited: Jul 16, 2013
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  4. Jul 16, 2013 #4
    LDC3

    Active Member

    Apr 27, 2013
    920
    161
    The large loop near the transmitter and has the label L2 on it.
    Good luck.
     
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  5. Jul 16, 2013 #5
    MrChips

    Moderator

    Oct 2, 2009
    17,132
    5,296
    OMG!

    Why would anyone build a gadget longer than it needs to be to hold a circuit board longer than it needs to be just because there is a copper trace that runs along the edge on both sides of the board that appears to do nothing?

    What is the frequency of RF transmission?

    This circuit was designed by an RF engineer who knew what he was doing. What makes you think you can increase the range with a better antenna?
     
    #5 Reply
  6. Jul 17, 2013 #6
    Etronic

    Thread Starter Active Member

    Oct 7, 2011
    127
    2
    Hi LDC3

    So the loop in the first photo label L1 bottom part of board is not part of the antenna.
    Or is it. It seems to be the same size.Do you think its connected to the loop L2.

    Is the varaible pot a cap or coil.Connected to trace label L2.
     
    Last edited: Jul 17, 2013
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  7. Jul 17, 2013 #7
    Etronic

    Thread Starter Active Member

    Oct 7, 2011
    127
    2
    MrChips

    Because I've done it a few times on other RF devices
    before.


    Don't Know.No Data on this item from Mfg.Could be 303Mhz-475Mhz.

    It might be 2.4Ghz. Because of the short loop.But i doubt it.Just don't know.

    They state it has a range of 450 Ft line of site. Not true.
    More like 200 Ft.
     
    #7 Reply
  8. Jul 17, 2013 #8
    KJ6EAD

    Senior Member

    Apr 30, 2011
    1,570
    441
    Look for an FCC identification number on the case.
     
    #8 Reply
  9. Jul 18, 2013 #9
    Etronic

    Thread Starter Active Member

    Oct 7, 2011
    127
    2

    Thanks for that information. I should of look at the label on the back of the case. The working FQ for this unit is 433.92Mhz. So my assumption was correct on the FQ as i stated in post #7.

    OK! So how do i measure for the correct antenna length. Any ideas.Or do i just use say 12'' wire 22G

    Also where would i place the wire on the loop label L2.Do i need to cut the trace anywhere on the loop.

    Somebody.
     
    Last edited: Jul 18, 2013
    #9 Reply
  10. Jul 18, 2013 #10
    Etronic

    Thread Starter Active Member

    Oct 7, 2011
    127
    2
    Originally Posted by KJ6EAD View Post
    Look for an FCC identification number on the case.

    Thanks! for that information. I should of look at the label on the back of the case. The working FQ for this unit is 433.92Mhz. So my assumption was correct on the FQ as i stated in post #7.

    OK! So how do i measure for the correct antenna length. Any ideas.Or do i just use say 12'' wire 22G

    Also where would i place the wire on the loop label L2. Do i need to cut the trace anywhere on the loop.

    Somebody.
     
    #10 Reply
  11. Jul 19, 2013 #11
    KJ6EAD

    Senior Member

    Apr 30, 2011
    1,570
    441
    The nominal length for a quarter wave dipole antenna at 433.92 MHz would be 173mm.
     
    Last edited: Jul 21, 2013
    #11 Reply
  12. Jul 21, 2013 #12
    DickCappels

    Moderator

    Aug 21, 2008
    4,967
    1,512
    If this is the circuit I think it is, the loop is tapped and power supplied at that point. If there is not already an inductor in series with the power supply, add one. I usually use 700 nh ferrite beads for that frequency range. Connect a small antenna to the point where the inductor connects to the loop.

    Notice that Y1 is not installed, meaning that oscillation frequency is determined by the resonant frequency of the loop and the variable capacitor. If you modify the circuit, the transmitting frequency will shift.

    Also, if you modify the circuit you will probably violate some law, depending upon where you are.
     
    Last edited: Jul 21, 2013
    #12 Reply
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