There are lots of possible problems. This page is a collections of some hints to find and fix possible problems.

To find this problem put your system in continuous power mode. If the shooting LED of the gun is not on then you have a problem.

1. Use an oscilloscope to make sure that the input to the transmitter board has an amplitude of 3.3V.
2. Check the gun to make sure that the gun LED is working. A gun tester was built to help with this diagnosis.
3. Check the supply voltage of your transmitter board.

With system set in shooter mode you should be able to point the gun at various different light sources (fluorescent lights, sun, monitor, etc.) and not record a hit. If a hit is recorded without it being shot (called a false positive) then the 'Fudge Factor' needs to be increased.

Increasing the 'Fudge Factor' reduces your maximum range. To decrease the 'Fudge Factor' you need to investigate the noise signals. The oscilloscope is the best way to sample your noise signal. The oscilloscope probe should be paced after the receiver board and the oscilloscope FFT should be used.