problem with TSOP 1738

hiii............
i am a new beginner in field of robotics........i am making the robot
for obstacle detection....i m using the TSOP1738 for the same ....
so i hv to generate a 38KHZ square wave ..........so,i m using 555 timer in astable mode....i m using r1 and r2 as 520 ohm and c1 as 0.02uf and 1N4148 diode ...............but my CIRCUIT is not working ...i think that i m not getting the 38KHZ signal by 555 . i also checked my circuit with r1 and r2 as 18K AND c1 as 1 nf and with the same diode.... can any1 tell me the
value of resistor and capacitor so that it would work correct ...........
it wud be better if u give the circuit diagram also....
thanks

What's with all the .............

Post your schematic.

Please attach the schematic of your 555 circuit.

A TSOPxxx IR receiver has automatic-gain-control that reduces its gain when there is a continuous ultra-sonic IR signal instead of the expected bursts of data.
The datasheet tells all about it even with some graphs.

Please show how your TSOP1738 is powered and how it is loaded.
The datasheet talks about powering and loading too.