transmitter using VCO

HI..I'm new in RF world but i'm try to learn it...
how to transmit audio using VCO (freq. Modulation) and how to demodulate it..? What is VCO? how it's work ?what the meaning og envelope detector, integrating?
Sorry if there to much question.....

Elits :)

VCO : voltage controlled oscillator
is a kind of oscillator, that is enable to change its frequency
due to some external voltage applied across it.
A probably most important component is a varactor diode.
You can refer a book about varactor diode. If you apply
a varying voltage across it, the capacitance of the diode
will change in it rhytmus, so with a fixed inductor you can alter
the frequency.
To demodulate an FM signal, you can use a frequency discriminator,
simply saying, you need a filter with linear flank.

regards

http://www.radioelectronicschool.com.../reading34.pdf