The following posts explains how to build a simple to build FM stereo transmitter circuit using IC BA1404.
About the IC BA1404
An exceptional stereo audio FM wireless transmitter circuit is presented below.
The circuit relies upon the IC BA1404 from ROHM Semiconductors.
BA1404 is a monolithic FM stereo modulator which includes integrated stereo modulator, FM modulator, RF amplifier circuitry.
The FM modulator could be controlled from 76 to 108MHz and power source for the circuit could be nearly anything between one.25 to three volts.
Circuit Operation
In the circuit R7, C16, C14 and R6, C15, C13 makes the pre-emphasis system for the right and left stations respectively.
This is achieved for complementing the frequency response of the FM transmitter with the FM receiver.
Inductor L1 and capacitor C5 is employed to fix the oscillator frequency. Group C9,C10, R4,R5 enhances the station splitting up.
38kHz crystal X1 is linked between pins 5 and 6 of the IC. Composite stereo reception is formed by the stereo modulator circuit employing the 38kHz quartz regulated frequency.
Construct the circuit on a high quality PCB.
Operating the circuit from a battery pack minimizes disturbances.
Work with an 80 cm copper cable as antenna.
For L1 try to make three turns of 0.5mm dia enamelled copper wire on a 5mm dia ferrite core.
Stereo FM Transmitter Circuit Diagram
Hello Sir, I Like This Circuit, And I Want To Construct It, But I Have Some Questions To Ask
1. For Instance If I Dont Get 38khz Crystal Oscillator, Can I Generate 38khz From 555 Timer And Feed It To The Circuit? And Can It Work Normal Like For Crystal Oscillator?
2. Can It Be Modified By Adding Press Botton For Scanning Or Selecting The Frequency?
3. Can We Add A Power Indicator Led To It?
4. Can It Be Modified By Adding Sound Indicator Circuit To It?
Solomon, we use crystal to ensure extremely stable frequency which cannot be achieved using ICs like 555, so it might not work.
You may have to refer the datasheet of the IC to learn if any modifications may be possible or not externally.
Music level indicator can be added at the output side of the circuit
i made a BA1404 Stereo FM Transmitter but unable to found stereo FM receiver circuit . Please help me as soon as possible.
you can use your mobile phone’s FM radio…
Can I connect this circuit to the TV output Audio RCA connectors
it's for radio FM range….won't work for TV I guess…
Hello i got this IC but I used a different circuit and its not working out as expected in the first place how do I know the value of the frequency that is being transmitted?
Hello, It would be difficult for me to troubleshot without practically checking it…
you can check the frequency by capturing the transmission on any standard FM radio and then checking the frequency level on the tuning calibration of the radio.
though i would suggest creating an LCR meter using arduino..It is an easy build and helps to find transmission frequency.
What is the software for doing the simulation BA1404?
Checked it…The datasheet didn't help much….
try a longer antenna.
Currently using a 1.5m long one.
that's quite long and sufficient…not sure, there could some other hidden issue somewhere
OK, good, thanks for updating the info
Made this as you instructed….still not getting a clear reception and the audio transmission isn't recognizable. What should I do?
check the datasheet of the IC and see if there's any refinements to be done.
You said 5 turns initially, if I don't get correct transmission, should I increase or decrease the number of turns?
you will have to experiment with the turns because the original IC datasheet has not informed about the exact number of turns for the coil
ok……
Wait then i'm sending the link to ground fill pcb pdf and the silkscreen too….
This is the link to the shared folder on google drive:
https://drive.google.com/drive/folders/0B-5jjw-tjYplaGJuVjN5cGUxOWc?usp=sharing
yes that looks OK to me.
I have neither a ferrite core nor a variable inductor. Please post a way to use a static inductor with a 2-18pf variable capacitor.
…ferrite cored inductor is a must for the explained design
ok…made this circuit…but getting too much static. What do you think is the culprit?
Wait. I just found a 5mm ferrite core. But since I don't have 0.5mm copper wire. Would you please tell me the improvised version of this coil for SWG22 wire. I can make air core coils according to given values but I don't know how ferrite cores change the inductance value so please tell me how to make a coil with 5mm ferrite core using SWG22..Hope this will eliminate the static caused by my circuit.
Please tell me how make this inductor for 22SWG as 0.5mm copper wire isn't available in my city. SWG22 is 0.711mm wide. I have salvaged a 5mm ferrite core. How many turns should I make to use it as an inductor in this circuit?
0.5mm is not critical you can use any other gauge thicker than that….
use 5 turns initially
to prevent noise use PCB with grounded tracks
yes it must be ground filled type or "copper pour" type PCB to enahnce stability.
sorry I cannot check your PCB if it's posted in some other electronic website.
you can post in some free image hosting site, and send the link here
Can this circuit transmit up to 2km? I also want to design mobile Phone call jammer can u pls upload the circuit or show me the link to mobile call jammer circuit. Thanks
is crystal resonator necessary??
how to adjust frequency???
by altering C6