You've asked numerous questions regarding this transmitter circuit, so to help us help you, may I suggest that you make one thread to ask many questions on one circuit.
Why do you ask about the 2N3904 transistor in this circuit? It is a very common transistor over here.
Look in Google for the obsolete LM3909 IC and you will find some links where people show how to make one with a few transistors.
Or make your own multivibrator oscillator to turn the transmitter on and off and use a 3V battery.
But i want to save the trouble of making 1 and buy 1 instead .
The LM3909 is obselete so i think i will put another instead of LM3909
ill put a PIC12F in for IC1.
But i want to buy it from Internet so theres a little mess i cant choose from this page.
HElp me which 1 should i use?????
FROM THIS PAGE!!!!!!!!!!!!!! https://www.oomipood.ee/index.php?t=k_o&otsi=PIC12F&
The cheap 12F508 can flash an LED with the best of them.
You're going to need a programmer too.
A 12F629 or 12F675 are better all around 8pin PICs (14bit core and other perks)
The i/p versions are DIP and the easiest to work with for experimenting.
A programmer is how you get your program "burnt" on to the PIC. it's a device that goes between your computer and the PIC. It handles all the special signals, voltages and timing required to program a microcontroller.
There are many kinds from homebuilt $$ to professional $$$.
Edit: as Hero999 mentioned you'll need at least a 2.5V power supply, a couple of AA batteries will do nicely. **broken link removed** A Microchip PICStart Plus Development Programmer (old, slow & expensive)