What frequency range does the Automatic Direction Finder operate in?

What frequency range does the Automatic Direction Finder operate in?

• A. 100 to 400 MHz
• B. 2 to 4 GHz
• C. 30 to 300 MHz
• D. 1000 to 2000 MHz

Answer: (A)

Automatic Direction Finder receivers are designed to pick up signals from ground-based navigation beacons used for bearing information. In aviation, the main beacons used for this purpose are VHF navigation aids, such as VOR and Localizer, which operate in the VHF range around 108–118 MHz. To cover these common nav signals, the ADF is specified to operate roughly from 100 to 400 MHz. Frequencies outside this range are used for other systems (radar, satellite, higher-band communications) and aren’t the typical beacons an ADF needs to measure bearing from. So, 100 to 400 MHz best matches the frequency region where ADF navigation signals are found.

Automatic Direction Finder receivers are designed to pick up signals from ground-based navigation beacons used for bearing information. In aviation, the main beacons used for this purpose are VHF navigation aids, such as VOR and Localizer, which operate in the VHF range around 108–118 MHz. To cover these common nav signals, the ADF is specified to operate roughly from 100 to 400 MHz. Frequencies outside this range are used for other systems (radar, satellite, higher-band communications) and aren’t the typical beacons an ADF needs to measure bearing from. So, 100 to 400 MHz best matches the frequency region where ADF navigation signals are found.