ADF (Automatic Direction Finder) radio waves are propagated as ground waves and/or sky waves. Problems associated with ADF are inherent in the frequency range that ...

One of the earliest radio navigation systems was Radio Direction Finding (RDF). Introduced in the 1920s, RDF allowed pilots to determine the direction of a ground-based radio transmitter.

Click to open image viewer. IIIF provides researchers rich metadata and media viewing options for comparison of works across cultural heritage collections. Visit the IIIF page to learn more.

IIIF provides researchers rich metadata and media viewing options for comparison of works across cultural heritage collections. Visit the IIIF page to learn more. 3-D: 22 × 15.2 × 18.8cm (8 11/16 × 6 ...