Ok so in this instructable i will show you how to make the simples AM transmitter, it doesnt have a lot of range but i'm working on it, and If YOU find a way please let me know.
Ok so you will need the following stuff
-Tuning knob(variable capacitor)
-Antenna coil(i will post a How to on How to make one of these in the first step.
-680 Ohms resistor
-0.0022 Micro farads capacitor(0.022 also works)
-A C945 transistro(All the ones i've tryed so far have worked, as long as its PNP and low voltage
-A pair of old earphones.
-two 1.5 voolts batteries, and battery pack.
Notes, sometimes works as a metal detector :O
The first non-breadboard version:
The PCB i got from my PCB box, saw wich copper lines went where and soldered my components on it(i was lucky, it's a hard way to make stuff but it happened :))
an basicly just used hot glue to glue everything to a battery pack...
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Step 1: The Antenna Coil How To.
To make the antenna coil you will need the folloiwng
-two long strands of Copper wire like 3 meters each (with some sort of varnish isolating it)
then start wrapping the first starnd around the ferite and secure with electrical tape
then secure that loose bit with more electrical tape, and with that same tape put the other starnd of wire around the ferrite.
you will have four loose wires, conect the midle two together, so u have three loose wires(like the photo)
TIPPP: when you antenna coil looks like the one in the pic, with a lighter or match burn the tip of the wires(just like a second, just to remove the varnish...
WARNING!!!! the antenna coil shown on the pic has very litle wire, so it doesnt work. yours should have much more wire wrapped around the ferrite.
If you want(recomended) solder a single core plastic wrap wire to each of the loose copper wires(best for breadboard) and make the middle wire have a diferent colour(so u dont get confused)
Step 2: Making the Transmitter
right, We have the antenna coil all we need to do is start making it :)
Grab the transistor and place it so that the round thingy is pointed towards you
conect RED WIRE(minus of battery) but yours can be any colour you want.
to the same side of the transistor as u see on the pic! very important!!!!
Grab the 0.0022 micro farads capacitor and place either terminal of it on the middle terminal of the transistor, and the other somewhere else(as long as it doesnt touch anything else)
put the 470K resistor in the middle terminal of transistor aswell, and the other side somewhere else as long as it doesnt touch anything else
grab the 680 ohms resistor and place it once again to the middle terminal of transistor(cant touch anything else either)
grab the 100K resistor and place it in middle terminal of the transistor, once again cant touch anything.
Conect microphone to the 470K resistor and the left terminal of transistor(the one with the - polarity of battery)
And the middle wire of the antenna coil to the 100K resistor
connect green wires to the lateral wires of the antenna coil, and the tuning knob(the green wires closest to you on the pic(the ones on the back or just something else)
and connect another wire to the 100K resistor( this will be the + of the batteries)
A schematic for those that didnt understand anything i sayd...(all lol)
NOTESSS: With the old earphones you can cut the earphones off, and keep the cable and plug, conect the wires to the places where the Microphone is, and the plug to your MP3 Phone, PSP, i conected it to a pocket recorder.
Then get a radio(AM or short wave) tune to a station with no channel comming in, just static, turn on your transmitter, adjust the transmitter's tuning knob, untill you hear high pitched sounds fromn the radio, turn on your MP3, or whatever your using, and make the final adjustments, it should reach about 2 meters, not much but enough to impress some people, and there are ways to make it stronger... i just dont know 'em yet xD, anyways 2 meters is ok for something that will cost about 2$ to make... so good luck ;)