Perhaps the very very very old ones, but the modern types are completely integrated PLL oscillators with ceramic or crystal resonators and digital modulation...
A typical example may be found here: **broken link removed**.
But for a wireless microphone, why not use a FM radio as the receiver and build a simple low power FM transmitter? (Do keep in mind that this frequency is not open for general use.)
For example something like this: **broken link removed**.
Hi!
For 2.4GHz, I recommend MC13191 Freescale transceiver. They have a built in PHY level implemented, then for send/receive data is easy for developer.