MK120 Range

I have assembled the MK120 and it works, but the range is around 2cm. Is there a way to improve the range with components or anything else?

Under normal conditions (indoors, no sunlight or direct artificial light), it can go up to 4m. Please note that IR leds are highly directional. Slightest misalignment can trigger the output. Check assembly (resistor values, component orientation). Make sure power supply is up to spec. Use adaptor for prolonged testing and use. A too low or too high voltage can cause odd behaviour.