i need a supply to transmit FM signal up to 1W.i used 780x but performence of FM is not good. received audio has the tone "ooooeeee " not like when using pin. i think that the reason for tone is the problem of supply.
Ensure that it is decoupled on the input and output pins, as per the datasheet.
Other possibilities are that RF from your 1 watt transmitter is getting onto the supply line and upsetting the regulator, this will be due to poor layout/decoupling/screening.
when i used pin supply, the audio signal was quite nice . but when replace the supply by 780x for larger power in same PCB, it became so bad (tone "oooeee").i can't reduce this noise .
the above circuit i simulated and its power is up to 1.2W . it has a little difference from practical circuit. i forgot some problem when post that picture.