Antenna Range Amplifier

Discussion in 'Wireless & RF Design' started by davidGG, Dec 20, 2013.

  1. davidGG

    Thread Starter Member

    Dec 22, 2012
    51
    0
    Hello.
    I am trying to make an AM transmitter for my car so I can listen to my music when I'm driving (I don't have an AUX port).

    I have been successfully able to transmit to an AM radio, but the range is 2 feet AT BEST. How can I increase this range? When I move my antenna further away I get a lot of static and my audio signal becomes inaudible.

    I need maybe around 5 feet to reach my cars antenna from inside my car.

    Right now I am still working on the prototype. I am using a quarter wavelength monopole for my antenna. Are there any compact types of antennas that I can use in this situation? Having a quarter monopole at 1Mhz can get quite long.
    Yes I can always make an FM transmitter to have a smaller antenna but I am short on time and this AM transmitter is practically done.

    Any suggestions? Currently my transmitter operates at about ~8VDC 3mA when broadcasting.
     
  2. sheldons

    Active Member

    Oct 26, 2011
    616
    101
    schematics needed........
     
  3. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,386
    496
    Use casset tape adapter. That is what I did with my 97 Nissan Altima.
     
  4. davidGG

    Thread Starter Member

    Dec 22, 2012
    51
    0
    Sorry, here is the schematic.
    [​IMG]

    One question I have is that isn't the modulation supposed to be done by a dynamic operator such as a transistor? From this tutorial/schematic, the modulation is done by the op amp. Isn't an op amp considered to be a linear device? Or do both suffice?

    Here is the full video:
    http://www.youtube.com/watch?v=3I_e7gIyfQg


    My 2005 Corolla only has a CD player. Plus I want to learn something in the process.
     
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Ebay has tiny car MP3 players that plug into the cig lighter socket and transmit in FM stereo to your car radio. The one I saw was under $10.
     
  6. jmoffat

    Member

    Jul 18, 2012
    41
    1
    One question I have is that isn't the modulation supposed to be done by a dynamic operator such as a transistor? From this tutorial/schematic, the modulation is done by the op amp. Isn't an op amp considered to be a linear device? Or do both suffice?

    I have to agree. What I see is two signals being amplified concurrently by the opamp. The oscilligraph proves this. The output is an audio wave with an RF wave riding on it. An AM modulated wave has bilateral symetry above and below the x axis.

    The audio signal should be controlling the gain of the op amp.
     
  7. nerdegutta

    Moderator

    Dec 15, 2009
    2,515
    785
    Hi.

    I made this a couple of years ago. I plugged it into the 3.5mm speaker jack on the PC and then I tuned my earmuffs with radio into the frequency, while working in the garden around the house.

    This is a FM transmitter.
     
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