Lightsquared has a license to broadcast in the 1525-1559 MHz band. Since their transmitters are on the ground, the signals are powerful. GPS is 1559—1610 MHz.

Lightsquared has a license to broadcast in the 1525-1559 MHz band. Since their transmitters are on the ground, the signals are powerful. GPS is 1559—1610 MHz. These signals are very weak, since the transmitters are in orbit. The pissing match is that even though on paper the two ranges don't overlap, in practice the Lightsquared transmissions tend to stomp all over the lower end of the GPS range, which make various interested parties unhappy. There's additional humor in that while it's certainly possible to get around interference like this, in practice that's dual-use technology which can be used to evade military GPS jamming.