According to the TSOP1838 specification, this won't work reliably. Continuous modulation is suppressed by the automatic gain control. You'll need a second modulation.You need for ex. 555 ic oscillator for driving IR-led.
I guess, there's a difference between a RC jammer and reliable operation of the sensor. If you want to operate a similar device, I really suggest to notice the datasheet.Here is IR-Led transmitter with 555-ic for TSOP 1838 --frequency 38kHz
im doing line following robot , when the light falls on the black line