Hey world...

This is a instructable on wireless audio transmitter.In most of our day to day life we come across situation where we need a connect our iPod,mobile,laptop.....etc. to our sound system,but the major limitation is the cable that we need to connect.This probably happens if your sound system doesn't have a wireless connectivity option.i too had the same problem so i decided yo solve it...:-)
Basically its a adjustable FM transmitter that is designed to transmit sound waves to the radio receiver.We connect the transmitter to our device and use a old phone or FM receiver to connect to our sound system.This might seem odd as we are kinda broadcasting our-self but the range of the transmitter is limited to 800 meters only.The reason choosing this option is that it is very very CHEAP ..!!Also u can connect multiple sound systems at a time without any worries of sync.Hope this project helps you.!

Step 1: Electronics You Need

Parts List :

Resistors :

R1 - 10k

R2 - 15k

R3,R4 - 4k7

R5 - 68E(68 ohms)

R6 - 2k2

R7 - 10E(10 ohms)

Capacitors :

C1 - 2.2uF/25v

C2,C3 - 10KpF(103)

C4,C5 - 10pF

C6,C7 - 1KpF(102)

Transistors :

Q1 - BC548

Q2 - C2570

Inductors (air core):

L1 - 4 turns (22 S.W.G Copper wire)

L2 - 4 turns (22 S.W.G Copper wire)

L3 - 6 turns (22 S.W.G Copper wire)

Miscellaneous:

Trimmers 1,2,3 - 22pf

Antenna - 30 cm

MIC (optional) - condenser MIC

Audio Jacks:

3.5 mm mono jack

3.5 mm female jack

6.5 mm mono jack (guitar jacks)

6.5 mm female jack

Step 2: Tools You Need

Tools :

Soldering iron

Soldering wire

Multimeter

pliers

Wire stripper

Tester

Fevi-Col

De-soldering pump

PCB hand drill (if needed)

Step 3: Schematics for the Transmitter

The above Image shows the transmitter Schematics you'll need to make the PCB.I have used a black zero PCB i.e. one that is used make a new prototype ;-).In the schematic instead of the MIC you can use a Mono jack. The pinouts for the jack are given above.Its has only two pins GND and Signal.The antenna can be replaced with a simple wire

Step 4: After Building the Transmitter

You should get this after building the PCB. I've used a plastic box to place the circuit.The transmitter has a 2 basically a 2 stage transmitter having a V.H.F. oscillator and a R.F. power amplifier.R.F. output power is 100 milliwats. Frequency of the Transmitter can be set with in 88- 108 MHz band by adjusting the first trimmer and also by adjusting the distance between the coil.Adjust the other 2 trimmers for max radiation.Connect a 9 volt battery and thats about it..!

Step 5: Applications

I had small speakers which I've connected to the speakers as radio receiver we can even use a FM receiver too. The tab is connected to the transmitter . So now whatever the tabs audio output is, it is being broadcast and received by the receivers.Also if you have to many transmitter in the at one place just change the frequency of the transmitter.
Here's a video of that.You can connect multiple sound systems now, by just getting a new receiver to each sound system.