DF North Offset Drone Test Module (NODTM)

General Dynamics Mission Systems performs periodic preventative and corrective maintenance on all of its Rescue 21 direction finding (DF) radio towers for the U.S. Coast Guard. A new true north offset line of bearing must verify direction during tower maintenance. Previously, the costly process involved sailing a boat along a specific path or driving a vehicle on difficult terrain to take measurements with specialized equipment.

This project presents a lightweight, modular attachment for a drone that effectively and efficiently calibrates DF radio towers.

The design attaches a small module with data recording/measuring capabilities to a DJI Mavic Air Drone. Drone pilots toggle on power to the module, activating the Arduino microcontroller and initiating data recording. As the DF North Offset Drone Test Module (NODTM) transmits very high frequency (VHF) signals at specific time intervals during flight around the tower, it simultaneously records and stores position, time and duration data. The data is exported as a single log file and post-processed to produce a DF tower calibration.