Part 1: Radio Direction Finding – The Foundation
Here's a practical example to cement these definitions. You're flying near Vienna and you need help with navigation. You call Vienna Radio for a bearing.
VDF Request and Bearing Reception
Vienna Radio · OE-FDC
FREQUENCY: 118.4 MHz
PILOT: Vienna Radio, OE-FDC, REQUEST QDM to Vienna station.
ATC OE-FDC, Vienna Radio, STAND BY.
PILOT: STANDING BY, OE-FDC. [10 seconds pass while the station takes a bearing]
ATC: OE-FDC, your QDM is two-seven-zero.
PILOT: QDM two-seven-zero, OE-FDC.
When requesting a bearing:When requesting a bearing:
You now know you should fly magnetic heading 270° to reach Vienna. If you fly that heading, the station will disappear behind you (assuming you're going away from it now, or approaching it from the east). The reciprocal QDR would be 090°—if you turned around, that's the heading away from Vienna.
Let's try another one where you're already near the station.
VDF Request Near Station
Vienna Radio · OE-ABC
FREQUENCY: 118.4 MHz
PILOT: Vienna Radio, OE-ABC, REQUEST QDR from Vienna.
ATC OE-ABC, Vienna, your QDR is zero-nine-zero.
PILOT: QDR zero-nine-zero, OE-ABC.
Recording a VDF bearing:Recording a VDF bearing:
This tells you that from Vienna's perspective, you're currently 090° (east) of the station. If you continue on that heading, you'll fly away from Vienna. The magnetic heading TO the station (QDM) would be the opposite: 270°.
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