Hi,
There are single chip audio video modulators on the market like:
TA1243, TA1297 from Toshiba, TDA8722, TDA8822 from Philips, TDA6060 from Siemens. These contain a rF oscillator, PLL circuit, and their RF section is suitable for the 470-860 MHz range (some of them goes down to 38.9 MHz IF frequencies). Some of them has a PLL for the audio oscillator. The RF output level is about 70-80 dBuV (aprox -37 to -27 dBm). But please note, all of these have double sideband.
This is not suitable for transmitting in the air. Read you the regulations of country. Normally the IF (38.9 or 45.75 MHz ) signal is frequency transponed to the final channel/ frequency, of course after the necessary (Vestigial Side Band) filtering. This signal then could be amplified to the necessary power level.
You can check the application schematics of the above mentioned manufacturers.
rgds, Al