wireless fm transmitter boost signal?

Discussion in 'Wireless & RF Design' started by lelejau, Feb 21, 2014.

  1. lelejau

    Thread Starter New Member

    Feb 21, 2014
    I recently purchased a wireless fm transmitter to listen to my songs in my car because my cd player doesnt support mp3 files. I found this alternative to be cheaper than buying a new cd player. But sometimes I hear a lot of static in the music background, sometimes interference...

    Is there any way to hack it to enhance its performance? I succeeded to identify the antenna but I am not an expert and not sure if I just add another wire to the end of the antenna to make it bigger. I also find out about limiting resistors and that I would need to remove that and add a new antenna to the device. Im not sure about what to do, I didnt want to buy a new device but try to make it better.

    I took some photos of the device to help identification.



    Closer look of antenna:


    This is how it looks like, unfortunately I could not find the exact model and name of this transmitter.
    Last edited: Feb 21, 2014

    Active Member

    Aug 8, 2011
    Since none of your PIX show an actual "antenna" , I am going to assume that there is not one coming out of the case.
    From your pix it would appear you have identified the antenna connection, you might try soldering a 20-22 inch piece of insulated wire to that point and see if that improves the signal.
    also , if the above works but you still need more signal , you might try wraping the antenna wire around the receiver coax coming from the receiver antenna .
    These type of transmitters/adapters are designed to only have an output of a few milliwatt's and to be used in very close proximity to the receiving antenna , adding more wire may get you more radiation from the transmitter but at some point you could get into rule violation issues with the FCC or your local version of the FCC, BE CAREFUL .
    There are products out on the market referred to as "WHOLE HOUSE" transmitters that run on 12VDC which have a bit more output which might work better for you but again BE CAREFUL , you do not want to be able to hear your transmitter 10 or 12 block's away (useful range is supposed to be limited to around 100 feet or so ( I don't know the exact rules here) .
    These can be found on "E-BAY" or Google them.
    Good Luck !
  3. k7elp60

    Active Member

    Nov 4, 2008
    You might check the tuning of your receiver in the car, it might be off frequency a little. Also if the FM transmitter is an imported unit the channel spacing may not be for US and the channel steps in USA are 100khz
  4. lelejau

    Thread Starter New Member

    Feb 21, 2014
    Well I am not from USA (I'm from brazil) so I don't really care about FCC legal stuff. Even if I raise the power, its not like I'm going to make a home radio and generate interference with the legal radios. even if I cause interference, I'll be on moving (driving) so it will be for a very short period.

    The tuner in my car is exactly the same as the transmitter, nothing wrong about that.

    Shouldn't I remove somekind of resistor to stop limiting the output power? If yes, how can I locate it ?

    I don't want to buy a new device, because I already have this one. Maybe there is a hack to make it work better? I've seen videos of guys hacking their fm transmitter and attaching antennas to it but I can't find one for my model.
  5. radiohead

    Active Member

    May 28, 2009
    If you do locate and remove the resistor that limits the output power, you will likely burn out the final amp (transistor). The purpose of the resistor is to bottleneck or slow down the current flow through the transistor to prevent it from overheating. Try what PRFGADGET recommended before you destroy the transmitter.