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A 15 w FM transmitter schematic

2016-04-06 11:28  
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Next is a 15 w FM transmitter schematic display. The principle is very simple and very practical.In the simplest form you need 4 things. First an input device such as an amplifiler you also use with your home-stereo.You can also use a walkman. Details about input-devices in the page: “Input”. Second you need a regulated power-supply. In this case a 14-18 Volts/2,5-3,5 Ampere. One of the most influencial things you need is antenna and coax-cable. More about this later on. And finally the transmitter itself. You can devide the transmitter in two main parts: the oscilator and the amplifiler. The oscilator converts electric sound information into electromagnetic waves. The amplifiler gives these waves a bigger amplitude. The most often used technique to connect the components to each other is soldering them on a double sided copper-board. Another way is connecting the components floating. It is cheaper but very tricky. Below you see the copper-board layout(PCB ). 

15W Fm-transmitter

15W Fm-transmitter

To get this pattern in copper surface you use a acid bath. Use a water-resistant permanent marker to paint your own copper-board black in the pattern the shown above. Color the back side ompletely black. The grid-squares are 0,5*0,5 cm each.

Now a few basic rules for good soldering:
1. Use a special electronics-solderingrod with a slim top.
2. Use soldering-metal with an anti-oxidant-fluid core.
3. Don’t heat the components! Heat the connection-point on your PCB.
4. Make sure that the surface is not too smooth.
5. Don’t use too much metal.
6. Don’t let the soldering metal form a bridge beetween two copper-surfaces.
7. If you’re smart you start from the middle of your prepaired board.

Below the schematic. The yellow lines are pieces of copperboard that devide the transmitter in 3 parts. This is essential. Without them, internal interferrence will ruin your signal.




Transistors usually have 3 or 4 different wires comin’ out. If you connect these wires in the wrong way the transmitter won’t work. It may even explode. The picture below shows how to prevent from such an event.

Use 1mm AgCu wire. A coil like 7x/d=10mm/l=15mm, goes round 7 times, has an diameter of 10 millimeter and is long 15 millimeters. The best way to make a coil is to bend it around a pencil or other cilindrical shaped object tight. The diameter of the object is always d-coil minus 1 mm. In this case 9mm.  

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