Four Stage FM Transmitter

This FM transmitter circuit uses four radio frequency stages: a VHF oscillator built around transistor BF494 (T1), a preamplifier built around transistor BF200 (T2), a driver built around transistor 2N2219 (T3) and a power amplifier built around transistor 2N3866 (T4).

FM Transmitter circuit diagram

A condenser microphone is connected at the input of the oscillator. Working of the 1 Watt transmitter circuit is simple. When you speak near the microphone, frequency-modulated signals are obtained at the collector of oscillator transistor T1. 

The FM signals are amplified by the VHF preamplifier and the pre-driver stage. You can also use transistor 2N5109 in place of 2N2219. The preamplifier is a tuned class-A RF amplifier and the driver is a class-C amplifier. Signals are finally fed to the class-C RF power amplifier, which delivers RF power to a 50-ohm horizontal dipole or ground plane antenna.
Use a heat-sink with transistor 2N3866 for heat dissipation (Note: or 2N4427 because it works better at 12 V and delivers up to 1 watt RF power). Carefully adjust trimmer VC1 connected across L1 to generate frequency within 88-108 MHz. Also adjust trimmers VC2 through VC7 to get maximum output at maximum range.
Regulator IC 78C09 provides stable 9V supply to the oscillator, so variation in the supply voltage will not affect the frequency generated. You can also use a 12V battery to power the circuit. Assemble the circuit on a general purpose PCB. Install the antenna properly for maximum range.
Coils L1 through L5 are made with 20 SWG copper-enamelled wire wound over air-cores having 8mm diameter. They have 4, 6, 6, 5 and 7 turns of wire, respectively.

200mW FM Transmitter

Here is the latest and greatly improved TX200 VFO/VCO FM transmitter. The most versatile transmitter to date that can be turned into high fidelity stereo PLL based 200mW FM transmitter. It is a perfect circuit for transmitting your music around the house and yard. TX200 uses only two coils; one in the oscillator and the other one in the 200mW VHF amplifier so it should be fairly easy for anyone to build. It also includes built-in pre-emphasis and C5 
for enhanced sound quality. While assembling the transmitter care must be taken to make sure that C1 is directly connected to L1 and C9 to L2. These caps eliminate the distortions form the DC supply and improve the sound quality greatly. 9V voltage supply is also very important because it provides the exact amount of current to Q1 to produce loud and clear sound quality. I hope that you'll have as much fun as I had while building this transmitter

If you want to use Phase Locked Loop (PLL) to digitally tune the frequency of TX200 then you will need to make small changes to the transmitter's oscillator. Theoretically, change original variable frequency oscillator (VFO) to voltage controlled oscillator (VCO). PLL uses voltage to change the capacitance of the varicap diodes / frequency of the oscillator so two BB105 varicap diodes or any 15-30pF varicaps will be perfect for this.

You vary the capacitance of the varicap diode(s) by applying voltage supply between 1 - 8V. If you apply 1V the capacitance will be around 34pF, and if you apply 8-30V the capacitance will be 12pF (minimum). Now, you may wonder why do we need to start from 1V? The reason is that if you apply voltages below 1V the capacitance may go as high as 200pF and we simply can't use that. 100K resistor will be used to lower the current of the voltage, because varicaps require only 0.2mA of current to operate!

With this knowledge we replace C6 - 15pF capacitor with two varicaps and one resistor. That much is enough to be able to use 1 - 8V voltage to change the oscillator's frequency. The second change that we will need to make is to use 2pF capacitor and connect it to the Q2 transistor's collector. PLL will use this to sample the frequency and compare it with digitally selected frequency. PLL will then compare those frequencies and if they are not the same PLL with vary the voltage that is applied to the varicaps, until those two frequencies are the same.

Before you even connect PLL circuit to the TX200 transmitter you will need to test if the oscillator is working properly. We can tune through entire FM band (88-108MHz) by applying the voltage to the varicaps. To do so, connect "PLL - Voltage Control" PIN to the 10K potentiometer as shown below. With this setup you will be able to use potentiometer to change the frequency of the transmitter. If you can't go through the entire FM band or if your frequency is out completely then you will need to change the inductance of the L1 coil.

Pemancar Fm 88-108Mhz IC-MAX2606

This is an mini fm Radio transmitter circuit. The supply voltage is between 1.1 – 3 Volts with power consumption is 1.8 mA at 1.5 Volts. This circuit should be able to cover 30 meters of range max. at 1.5 Volts.

mini FM transmitterSkema rangkaian mini FM transmitter


Note:
* Use a battery for powering the circuit.It will reduce noise.
* An FM antenna from a old radio is a better option than the wire antenna.



PN2222A transistor description

This device is NPN General Purpose Amplifier for use as a medium power amplifier and switch requiring collector currents up to 500mA.

Absolute Maximum Ratings.
  • Collector-Emitter Voltage (VCEO ) : 40 V.
  • Collector-Base Voltage (VCBO) : 75 V.
  • Emitter-Base Voltage (VEBO) : 6.0 V.
  • Collector Current (IC) 1.0 : A.
  • Operating and Storage Junction Temperature Range (TSTG) :- 55 ~ 150 °C.
  • Collector-Emitter Breakdown Voltage : 40 V.
  • Collector-Base Breakdown Voltage : 75 V.
  • Emitter-Base Breakdown Voltage : 6.0 V.

Pemancar FM dengan IC BA1404

Jadilah "On Air" dengan stasiun radio sendiri! Pemancar FM Ini merupakan produk menarik yang akan menyiarkan sinyal stereo berkualitas tinggi dalam 88 - 100MHz FM band. Hal ini dapatdihubungkan ke semua jenis sumber audio stereo seperti komputer pribadi, CD player, walkman, televisi, tape deck atau sistem stereo untuk mengirimkan suara stereo dengan kejelasan yang sangat baik di seluruh, kantor Anda pekarangan rumah, atau tanah kamp.
Hal ini juga dapat digunakan dalam mobil untuk memutar CD melalui radio mobil Anda ketikamelekat pada CD player pribadi. Aplikasi lain dapat mendengarkan stasiun radio satelit melaluiradio FM. Selain itu, dapat dihubungkan ke komputer pribadi atau laptop untuk memungkinkanmendengarkan stasiun radio internet atau pra-rekaman musik digital (seperti file MP3).



Sirkuit yang mencakup snap baterai 9V dan stereo 3.5mm jack dipasang tepat di papan tulisuntuk koneksi yang mudah ke sumber audio. Sebuah ON / OFF serta "On-Air" indikator LED juga dimasukkan di papan tulis.
 

Source : http://home.maine.rr.com/randylinscott/feb98.htm
   
Rangkaian ini didasarkan pada IC BA1404 penyiar stereo populer yang berisi semua sirkuit kompleks untuk menghasilkan sinyal FM stereo. Sebuah kristal KHz 38 menyediakan stabil sub-carrier untuk sinyal stereo. Rangkaian osilator cukup stabil untuk penerimaan handal bahkan di radio FM digital disetel. Penyesuaian input terpisah kanan dan kiri tingkat juga disertakan.

Untuk memperoleh Kit ini anda bisa membelinya di CAR'L ELECTRONICS

Lampu kunang-kunang

Kunang-kunang adalah sejenis binatang serangga yang di ekornya bisa mengeluarkan cahaya. Cahayanya bisa terlihat jelas pada malam hari. Cahaya yang dikeluarkan warnanya ada yang merah, kuning dan hijau. Kebanyakan yang kita lihat adalah warna hijau terang. Untuk melihat kunang-kunang sekarang sudah mulai sulit karena habitatnya sudah mulai rusak. Untuk mengobati kerinduan akan kehadiran kunang-kunang, kali ini saya akan memberikan skema Rangkaian Lampu kunang-kunang untuk anda. Rangkaian ini cukup sederhana sehingga cocok sekali untuk anda yang masih pemula dalam elektronika. Rangkaian ini menggunakan cahaya LED sebagai cahaya yang menyerupai kunang-kunang.

Skema Rangkaian Kunang-kunang
Gambar rangkaian kunang-kunang
Daftar Komponen:

U1 = NE 555 Timer IC
R1 = 10K,
R2 = 2M,
R3 = Potensiometer, 1M
C1 = 10uF, 25V,
D1 = Dioda, BAS16, atau IN4148,
D2 = LED, hijau warna cerah
Baterai Standard 9 Volt

Rangkaian kunang kunang ini bisa anda tempatkan di dinding kamar sebagai hiasan. Bisa anda tempatkan sedemikian rupa pada wadah yang kecil atau kotak sehingga yang terlihat nanti adalah lampu LED nya. Selamat berkreasi!
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