Stereo FM transmitter using BA1404

Stereo FM transmitter circuit using BA1404.

Notes.
A high quality stereo FM transmitter circuit is shown here. The circuit is based on the IC BA1404 from ROHM Semiconductors. BA1404 is a monolithic FM stereo modulator that has built in stereo modulator, FM modulator, RF amplifier circuitries. The FM modulator can be operated from 76 to 108MHz and power supply for the circuit can be anything between 1.25 to 3 volts.
In the circuit R7, C16, C14 and R6, C15, C13 forms the pre-emphasis network for the right and left channels respectively. This is done for matching the frequency response of the FM transmitter with the FM receiver. Inductor L1 and capacitor C5 is used to set the oscillator frequency. Network C9,C10, R4,R5 improves the channel separation. 38kHz crystal X1 is connected between pins 5 and 6 of the IC. Composite stereo signal is created by the stereo modulator circuit using the 38kHz quartz controlled frequency.
Circuit diagram.

stereo fm transmitter

Stereo FM transmitter circuit

Notes.

  • Assemble the circuit on a good quality PCB.
  • Powering the circuit from a battery will reduce noise.
  • Use an 80 cm copper wire as antenna.
  • For L1 make 3 turns of 0.5mm dia enamelled copper wire on a 5mm dia ferrite core.

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28 Responses to “Stereo FM transmitter using BA1404”

  • Darren says:

    Correct me if I’m wrong but left and right Line In are wired at the same point looks like it would combine the two rather than having an independent left and right speaker(stereo)

    • Darren says:

      …Ok my error I just see it properly the inside dot is + and the outer circle for line in is – so the only this it’s connected to is the ground between the two line ins

  • Abani says:

    I need a BA 1404 IC. Is it available in India ? Please give me the address. I’m ready to pay in terms of Indian currency.

  • Navneet raj says:

    can i use it with my fm receiver??

  • Steeven says:

    Hello,
    how can I variate the output frequency?

  • EVE Alain says:

    Hello,
    I am a professor of electronics in France, and I would like to work with my students on a stereo encoder.
    For that I would like two copies of 38 kHz quartz please.
    Can you send me.
    Thank you in advance.

  • abhay says:

    i found quality circuit at the same time i want all the component alogh with the pcb for Stereo FM transmitter using BA1404
    where should i purchase all the require component plz help

  • charles says:

    i want 2 have back room radio station , can you please me more about transmitters, especially how to built them to broadcast for a long distance.

    Can it be possible to make a radio mp3 broadcast a long distance without buying an external boaster?

  • jojo says:

    @Frednand

    Start your learning by trying out simple circuits like – lighting an LED

  • frednand francis says:

    I LIKE THESE CIRCUIT.BUT I WANT TO LEAN MORE ABOUT THIS ESPECIAL HOW TO MAKE THEM.WHAT CAN I DO?

  • ninzibarrientos says:

    sir how about monophonic transmission? is there any suitable or prefered circuit configuration?..thanks

  • ninzibarrientos says:

    how much is the inductance range /value of L1? can i replace it with different type but with the same value?

  • ninzibarrientos says:

    the freq comutation will still be equal to the computation for resonance freq of LC connected in paarallel? like fr=(2pi*sqrt(LC)^-1? how about some loading capacitance? do i still need to connect additional capacitor ? thanks

  • ninzibarrientos says:

    i thought if we’re using LC as osc. it is in parallel connection? so you mean if i replaced the xtal with LC the Lc will be in series connection? from 5-LC-6 and vice versa? or i do still need to connect the LC(as the osc)into the gnd/ground? can yo please send me the details on the connection? plz? and what if i use external osc? like for instance a 555 timer ic configured as osc.with 38khz oscillating frequency output…how or what will be the connection from pin 3 of 555 timer ic to the BA1404 pins for osc? thanks

  • seetharaman says:

    Hi Nin you can use series LC tuned circuit between Pins 5 and 6.

  • ninzibarrientos says:

    hmmm i see.. if i utilized the LC as the alternative component for crystal , does it will follow the same connection? like for instance the crystal is connected across pin 5 and 6 and in series with the capacitor as its loading capacitance..if i replace it with LC will i connect it similar to the crystal? with LC both in parallel to each other,in series with a capacitor and connected across pin 5 and 6?..thanks..pls reply me immediately

  • seetharaman says:

    Hi Nin you can try LC network than RC, but tuning is critical without proper test instruments. But the 38KHz crstal will be best.

  • ninzibarrientos says:

    i encountering a hard time looking for 38khz oscillator..can i utilized RC osc. instead? as an alternative or replacement for the said crystal oscillator?

  • seetharaman says:

    With the above transmitter and 1/2 wavelength antenna you can get the signal within the house. say within 50 feet or so. if you want higher range you have to feed the output of this IC to a 5watt or better RF amplifier.

  • mhz says:

    Left in and right in are audio inputs, of course.

    How’s the power and signal range with this transmitter? Could it be made for >1 km?

  • Venkatesh says:

    What is left in and right in

  • Newton says:

    am a researcher, a student studing electrical engineering networking and telecoms is my field.

  • pankaj says:

    it is very intresting circuit but i am unable to find 38khz cristal in agra please tell me any shop’s name in agra or delhi

  • sreejith kerala says:

    From where can I get BA1404 it is not available in our area(kerala, TN). can any one suggest a shop (with address) in south india !

    • saiyathu ibrahim says:

      hai sreejith ba1404 have in shop
      address:
      sunrise electronics
      coimbatore,
      tamilnadu,
      india

      “where can i get 38kHz crystal oscillator please tell me.

  • Buddhi says:

    Any information about L1 ??