@tylernt: thank you, now i understand!
@oric_dan: Pin13 has a buildin resistor, so far as i know. (Works for me ^^)
as i mention in the first post, i use this reciever: https://dl.dropbox.com/u/6634904/A500_TSOP312SERIES_DATASHEET%20(1).pdf
38kHz.
There is only a resistor in the connection to Vcc in the Datasheet (ApplicationCurcuit)
Do i also need a pullup?