Also, as far I know, the functional range of Bluetooth is less than 40 feet.
“Also, as far I know, the functional range of Bluetooth is less than 40 feet.”
That only has to do with consumer grade electronics. A receiver and antenna designed to pick up weak signals could pick up Bluetooth many miles away.
That’s for communication between two bluetooth devices, with low-power electronics (for long battery life) and a miniature antenna.
They were undoubtedly using a large antenna, perhaps several feet across, or an array of antennas. Also they were probably using military-grade receiver electronics that pull a lot of power from the helicopter’s electrical system. Together, those elements could be orders of magnitude more sensitive than an ordinary Bluetooth receiver.
But sensitivity means the noise gets amplified too; in this case, the “noise” includes other nearby Bluetooth devices; if they’re flying at altitude, “other nearby devices” could mean tens of thousands of others, at least in an urban or suburban environment. That’s what I’m having trouble understanding.