adding antenna to clock radio

Discussion in 'General Electronics Chat' started by lokeycmos, Jul 29, 2011.

  1. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    i need to solder on an external FM antenna to my clock radio. i attached some pics. there is a ferrite rod for am. but i cant see anything for fm. could someone please point out where i would solder the antenna to the board? TY
     
    • 1.jpg
      1.jpg
      File size:
      307.5 KB
      Views:
      103
    • 2.jpg
      2.jpg
      File size:
      310.8 KB
      Views:
      135
    • 3.jpg
      3.jpg
      File size:
      294.8 KB
      Views:
      95
    Last edited: Jul 29, 2011
  2. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    a few more pics
     
    • 5.jpg
      5.jpg
      File size:
      295.4 KB
      Views:
      79
    • 6.jpg
      6.jpg
      File size:
      292.8 KB
      Views:
      84
    • 7.jpg
      7.jpg
      File size:
      294.6 KB
      Views:
      70
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The FM antenna is usually a short piece of wire from the circuit that is wrapped around the AC cord for a few turns.
     
  4. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    checked that already...nada
     
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    Looks to me that its the trace at the top of the board of picture 2. The one connected to the pad labeled "FM"
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The short trace on the pcb is too short for an antenna for the FM broadcast band. It should be near 80cm long like a long whip or like the power cord.
     
  7. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    does anyone know of a good site for schematics? it a GE 7-4813B. i did figure out that the FM antenna is coupled to the power cord. instead of the power transformer having 2 primary and 2 secondary leads, it has 6 secondary leads. some how the antenna is coupled to it throught the swirl traces. hoping i can find a schem. ty
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    You could try a 5' piece of wire with 1' run parallel to the power cord to see if it helps. You don't always need to connect an antenna directly to a circuit.

    If it works, but is still too weak, try 8', as that approaches the resonant length of 88Mhz.
     
  9. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The very cheap radio will be overloaded by strong local stations if its antenna is too good. Then the stongest stations will be all across the dial like my cheap Sony Walkman FM stereo radio (it has a local-distant switch that attenuates the antenna in the local position).

    The datasheet for Toshiba's TA2003 radio IC has recommended simple schematics of radios that use it.
     
  10. trader007

    Active Member

    Feb 27, 2010
    222
    19
    This is a bit of a thread bump, but my question directly relates to this topic.

    If you have a cheap radio (mine is a armband radio), and it uses the headphone cord as the antenna (like cellphones do), is there a way to add an external antenna?

    I have a reason for putting a tiny fm tuner in a custom boombox... but I dont know where I should hook up an external antenna.
     
  11. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
    744
    Pin 1 is the fm signal input, try following the track from there.
     
Loading...