The transmitter I'm building is based on this schematic:
It's stable and has output of 15-18 watts. This enough to terrorize your
wide
surroundings at the fm-band.
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).
I designed it looking closely at the root scheme.
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.
When the acid has eaten the non-painted copper away you must remove the
complet thin layer of black paint with sandpaper. Don't remove too much copper
with it.
So, now you have the surface to solder the electric components on.
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.
In this way you'll have enough space.
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.
This picture is the coldwater-version... For the detailled version:
There are some components that need extra attention. 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.
You can find the numbers and letters back in the soldering schematic.
Coils also require extra attention. You can buy the coils trough ferrite in the
shop, but
the other ones have to be made yourself. 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.
As I said: bend the wire round (in this case 7times) with the revolves tight
together.
To get the desired length stretch the coil when still around the pencil
If you decide to build the transmitter and buy the parts, this list will
be handy:
