Apakah Anda ingin membuat sendiri stasiun radio, menyebarkan musik di sekitar rumah, atau hanya membuat sebuah link nirkabel antara iPod dan unit penerima di mobil Anda, pemancar ini akan memungkinkan Anda melakukan hal ini dengan mudah. Dengan BA1404 HI-FI Stereo pemancar Anda akan dapat mengirimkan MP3 musik dari iPod Anda, komputer, discman, Walkman, TV / SAT penerima, dan audio banyak sumber lain.

Pemancar FM di atas desain merupakan hasil dari banyak jam pengujian dan tweaker. Tujuannya adalah sederhana; untuk menguji banyak yang ada BA1404 pemancar desain, membandingkan kinerja mereka, mengidentifikasi kelemahan dan datang dengan desain baru BA1404 pemancar yang meningkatkan kualitas suara, telah sangat baik frekuensi stabilitas, memaksimalkan jangkauan pemancar ini, dan sangat mudah untuk semua orang untuk membangun. Kami gembira mengumumkan bahwa tujuan dan harapan ini telah bertemu dan bahkan melebihi.

Layan dapat bekerja dari satu 1.5V sel baterai yang sangat baik dan memberikan jernihnya suara stereo. Ia juga dapat diberikan dari dua sel baterai 1.5V untuk memberikan maksimum jangkauan.
Salah satu kualitas BA1404 pemancar FM adalah stabilitas frekuensi yang sangat baik. Hal ini terutama disebabkan oleh penggunaan yang berkualitas tinggi 3,5 gilirannya variabel berliku-liku. Merdu coils RF yang ideal untuk frekuensi tepat karena besi kawat itu tertanam dalam plastik, yang mengurangi frekuensi drifts. Reguler udara coils tidak profesional yang dipilih untuk penyiaran karena lilitan memperluas pangsa pasar dan kontrak dengan perubahan suhu. Itulah alasan mengapa sangat berliku-liku variabel telah dipilih sebagai substitusi untuk udara dan berliku-liku Kondensator variabel.

Lain kualitas yang disajikan BA1404 pemancar adalah jernihnya suara stereo dan meningkatkan pemisahan suara. Ada beberapa faktor yang rekening untuk meningkatkan kualitas suara dan pemisahan. Pertama adalah alasan penggunaan 38 KHz kristal yang menyediakan batu solid frekuensi untuk Encoder stereo. Alasan lain adalah penggunaan dua 1nF decoupling kapasitor untuk satu BA1404 chip dan lain untuk gulungan 3,5 variabel. Kapasitor ini harus mungkin dengan sebuah chip BA1404 dan berliku-liku karena variabel ini akan sangat meningkatkan kualitas suara, suara dan bahkan pemisahan frekuensi stabilitas juga. Apa yang mereka lakukan adalah menyaring kebisingan masuk dalam tegangan DC. Jika kebisingan memasuki BA1404 chip stereo generator akan memasukkannya dalam mempengaruhi suara yang dikirim baik suara dan multiplex sinyal yang bertanggung jawab untuk generasi yang jelas sinyal stereo. Jika suara itu akan memasuki juga disertakan dalam generasi subcarrier frekuensi yang mempengaruhi stabilitas frekuensi. Kebanyakan orang tidak menyadari betapa pentingnya dan mungkin ini adalah tempat mereka di lokasi yang salah, jauh dari target yang menyediakan komponen tidak digunakan, atau bahkan memutuskan untuk tidak menggunakan kapasitor ini sama sekali.

Faktor lain yang sangat penting dan yang meningkatkan kualitas keseluruhan dari seluruh BA1404 pemancar frekuensi termasuk stabilitas, suara dan kualitas suara adalah pemisahan penggunaan tanah pada pesawat pemancar PCB's. Dianjurkan bahwa tanah pesawat harus selalu digunakan di sirkuit yang berurusan dengan frekuensi yang lebih tinggi.

Ini yang disarankan resolusi tinggi untuk tata letak PCB BA1404 pemancar. Siap untuk dicetak dan tidak diperlukan penyesuaian lebih lanjut. Dimensi dari PCB harus 57 mm x 35 mm (W x H).

Download layout in Photoshop format (600 dpi)
Download layout in TIFF format (600 dpi)

Where to get the Parts

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If you are building the above Stereo FM Transmitter and have trouble finding some of the components like BA1404, 38KHz crystals and 3.5 turn high precision variable coils we are distributing the following components in our Electronic Store and a complete list of parts in Electronic Kits section.

Fox hunting Antena



Dimensi-nya sebagai berikut :

Element	Length (M)	Spacing (M)	Diameter (M)
Reflector	1.029	0.0	0.005
Driven element	0.981	0.311	0.005
Director	0.930	0.622	0.005

Resistors :
R1 - 68 k
R2 - 22 k
R3 - 180 k
R4 - 10 M
R5 - 10 k
R6 - 47 R
R7 - 240 k
R8 - 1,5 k
R9 - 820 R

Capacitors :
C1 - 100 p (ceramic)
C2 - 1 n (plastic)
C3, C6, C12 - 100 n (ceramic)
C4, C11, C13 - 100 u (electrolytic)
C5 - 0,33 u (tantalum)
C7, C8 - 10 u (electrolytic)
C9 - 220 n (plastic)
C10 - 47 n (ceramic)
C14 - 470 n (plastic)

Misc :
T1 - BF245C
T2 - BC556B, BC307
IC1 - LM386

Layout PCB atas

Layout PCB bawah

500mW FM PLL transmitter 88-108MHz
This is strictly an educational project explaining how a transmitter works and can be built.
According to the law it is legal to build them, but not to use them.
This transmitter is PLL controlled and the frequency is very stable and can be programmed digitally.
The transmitter will work from 88 to 108 MHz and the output power is up to 500mW.
With minor changes the frequency can be set from 50 to 150 MHz.
All contribution to this page are most welcome!

Background
FM transmitters have always been fascinating and one can find thousand examples of them on the internet.
Sadly most of them are full of error and miss leading information. Most of them also have low stability and frequency drift, many coils and components which are difficult to find.
The output power is often set to several watts with just a transistor or two…..can't fool me..
So therefore I decided to construct a simple transmitter with great performances.

Some contruction achievements I wanted were:

Simple construction

Commonly components

High quality and stability

Low number of coils

High output power

The frequency of this transmitter can easy be changed with software and space/compress an air coil, simple don't you say?
The basic hart of this transmitter is a colpitts oscillator. The oscillator is a VCO (voltage controlled oscillator) which is regulated by a PLL circuit and PIC micro controller. Don't get upset now…it is not that difficult after all.
Let's check the schematic and I will explain the function.

Hardware and schematic
The main oscillator is based around the transistor T1.
This oscillator is called Colpitts oscillator and it is voltage controlled to achieve FM (frequency modulation) and PLL control. T1 should be a HF transistor to work well, but in this case I have used a cheap and common BC817 transistor. The oscillator needs a LC tank to oscillate properly.
In this case the LC tank consist of L1 with C1, C2, C3, and the varicap BB139.
The coil is parallel with C1 and C2 which are in serial . The same with the varicap and C3.
You can think that L is parallel with [ (C1//C2) + (Varicap//C3)]
The value of C3 will set the VCO range. The large value of C3 the wider will the VCO range be.
Since the capacitance of the varicap is dependent of the voltage over it, the capacitance will change with changed voltage. When the voltage change, so will the oscillating frequency.
In this way you achieve a VCO function.

PLL and Microcontroller
The oscillator is made to work as "Voltage Controlled Oscillator" VCO.
To control the frequency a synthesizer circuit LMX 2306 has been added. The PLL circuit has a pickup coil (L2) connected to pin 6.
This coil should be put close to the L1 coil for picking up some of the oscillating energy.
The PLL in the LMX2306 will then use this frequency to regulate the VCO and lock it to desired frequency.
The regulating system also need an external reference crystal. In this case I use 12.8 MHz.

At pin 2 of MX2306 you will find a PLL filter to form the V_out which is the regulating voltage of the VCO.
The PLL try to regulate the V_out so the oscillator keeps the frequency locked to desired frequency.
The desired frequency is programmed into the PIC EEPROM and is clocked into the synthesizer (LMX2306) at power up.
I will below explain how to program the EEPROM for different frequencies.
At pin14 of the synthesizer you have a control output. At this output you will find the reference frequency for testing.
(I must warn you because the signal is not symetrical in shape. The positive pulse are only a few microsecond so you will have difficult to see it at oscilloscope.) I solved it by connecting it to a 74HC4020 (14-stage Binary Counter) to pin 10 Clock input. At Q0 (pin 9) you will have a symmetrical square wave with half frequency since the circuit is a counter. At Q1 pin 7 it will be divided by 4, see datasheets for more info.

LF input
The audio you wish to transmit should be connected to the Audio input (left side of schematic).
The signal will affect the varicap and thereby Frequency Modulate FM the RF carrier.
A potentiometer P1 has been added to set the modulation depth (Wide FM or Narrow FM). You may have to play a bit with the value of P1 because it tends to modulate to much. You may have to add a 500k - 1M potentiometer instead. You test and find out yourself.

Buffer stage
Here you find another HF transistor and it is working in class C.
The resistor R1 and the resistor Re2 set the DC current. In this case I found that 9.1k will give good output power and so the same with 150. If you wish to increase the power Re2 should be lower. You can add another 150 ohm resistor parallel.
In the table below I show you the output power with different voltages and values of resistor Re2.
I advice you not to run this transmitter with to high output power. The transistor I use is a small one and tends to get hot.
I advice you to run the unit from 0 - to 200mW. At 500mW the transistor will be in pain...*smiling*
At the output you will find a T network. This "filter" will match the antenna impedance to the transmitter output stage.
You have two variable capacitors 60pF to tune the transmitter for best performances.
The antenna I used I a 1/4 wave whip antenna (wire) about 75cm long.
This type of antenna is smaller but not so good performance as a dipole.
With a dipole you will be able to transmitter much longer distance.
How long can I transmit?
That is a very difficult question because the environment affect the transmitting distance very much.
In a city environment with concrete buildings the transmitter will send maybe 200m.
I an open filed it will transmit 2000m.
I did a filed test and with 70mW output power into the "bad" whip antenna placed indoors I could transmit 200-300m out into a park with no problem.

Output power
Table below show you the power measurements I have done.
The Re2 is 150 ohm and in some test I connect a 50 ohm parallel.
The output power in measured into a dummy load of 50 ohm.


Testing
The first thing you should test is that the oscillator is working. I disconnected the V_out from pin 2 of the PLL LMX2306.
I then connected V_out to ground and check the oscillator. The oscillator should now oscillate at the lowest frequency.
With my Wireless frequency counter I found that the oscillator was working at 100 MHz.
I streatched the coil L1 a bit until it oscillated at 105 MHz.
I then connected V_out to +5V and now the oscillator was oscillating at 108MHz. Great!, just as I wanted.
By changing the V_out from 0 to +5V I could change the oscillating frequency from 105 to 108 MHz.
I then reconnected the Vtune to the PLL.

Download PIC16F870 programs (INHX8M format)
The zip file contains several hex files made for different frequencies (88 to 108) MHz.

fm_500.zip

PLL software to FM transmitter (the hex files are zipped!).

Final word
This project is explaining how you can build a FM transmitter with great performances.
I advice you not to use it because it is not legal. You can only use it with a dummy load, not with an antenna.
If you choose to use an antenna I hope you will use it with good manner.

You can always mail me if there is anything unclear or need help with PLL frequency software.
I wish you good luck with your projects and thanks for visit my page.