RF rx\tx module

ok, i tried it; when i first push the transmitter's button, i get jump for -47dB to -27dB and back to -47
when i release it, the same thing happens
what do i conclude? how does that translate in volts? can i pick it up with a microcontroller?

i'm using about 1.5 meters of audio cable (high quality)

So it only gives you two states? one when the button is pressed and one when it isn't? (you can calibrate visual analyzer to give you voltage instead, play around with the settings, it's been a while since I've used it)

IT FINALLY WORKED!!!
ssssssss, well it worked because, i soldered my wire on the wrong pin o.o
Damn those chinese circuit boards!!!!

but a couple of days ago, you said that my transistor circuit can detect 3.4v as min
how did you calculate that??? it will help for my signal amp

and thanks alot for your help and that awesome piece of software

For a transistor to operate in the active region your base-emitter voltage should be about 0.7, this is kept relatively constant by the transistor for a large range of current, more is ok but less usually won't work, when this voltage is reached the transistor starts to amplify the current through the base. The same holds for a diode, it needs 0.7v as well, transistors and diodes are closely related, while a diode has one pn junction an npn transistor has two. Since a led is simply a special kind of diode it has the same characteristics but requires about 2v to turn on.

If you look at your circuit from your input pin it falls over 2 base-emitter junctions and a single diode so you simply add these together which gives you (0.7 + 0.7 + 2 = 3.4), note you could have used a single transistor. When a junction voltage is exceeded with a reasonable amount the device basically becomes a short which means that if you got your led to turn on it would effectively short your power supply blowing it instantly (presuming it wasn't just given a quick pulse). You need to include a resistor in series with your led to prevent this.

Most led's opperate best at around 20mA, presuming a 5v supply and 2v drop across the led you need a resistor of ((5-2)/0.02=150).

Since a transistor base-emitter junction is just a diode it has the same effect, if you simply hook it up to your supply it'll short out your supply so you need a resistor as well (between your amp input and the base of the transistor). Presuming your circuit we need to limit the current a bit, your circuit has an absurd amount of gain so just limit the current with anything you have at hand, not real reason to calculate it, a 1k should be fine.