What major advantage does ADF have over VOR systems?

The major advantage of ADF (Automatic Direction Finder) over VOR (VHF Omnidirectional Range) systems is that ADF is not limited to line of sight. ADF utilizes low-frequency radio signals, which can follow the curvature of the Earth and reflect off surfaces such as the ionosphere. This characteristic allows users to receive navigation signals even when they are beyond the line of sight of the transmitter.

In contrast, VOR systems operate in the VHF frequency range, which requires a direct line of sight between the transmitter and receiver. As a result, the effectiveness of VOR can be significantly impacted by obstacles such as terrain or buildings, leading to limitations in reception range, especially at lower altitudes.

This attribute of ADF gives it a particular advantage in terms of navigational coverage, especially in areas where VOR signals may be interrupted due to obstructions. Additionally, while ADF may have certain operational advantages in specific contexts, its inherent capabilities related to signal reception flexibility make it unique compared to VOR.