Over what distance will telemetry work?

The operational range of the telemetry modules depends largely on the conditions in which they are used. For best results, the antennas must be in plain sight of each other and one (or ideally both) of them raised far above the ground. 
 

Expected maximum range:

• Difficult environment (blocked by buildings or trees) - 150 – 300 m (500 – 1,000 ft).
• Open environment with antennas at ground level (clear view with antennas on car roofs) - 1,000 – 1,400 m (3,400 – 5,000 ft).
• Open environment with antennas at height (clear view with antennas mounted on masts of building rooftops) - up to 3,500 m (11,000 ft). This range has been measured at larger distances (10,000 m) when the antennas were on hill tops with line of sight.