Direction Finder Marconi-Bellini-Tosi Type No 11F

The Direction Finder for professional use Type No. 11F is similar to Type 11 and Type 11A but has one tube more. We are not sure about the valve types.

From Wikipedia: 
"BTDF was invented by a pair of Italian officers in the early 1900s, and is sometimes known as a Marconi–Bellini–Tosi after they joined forces with the Marconi Company in 1912. BTDF was the most prevalent form of naval direction finding from the 1920s to well into the 1980s and was used as a major part of early long-distance air navigation systems from the 1930s until after World War II. BTDF systems were also widely used for military signals intelligence gathering."

From mhs.ox.ac.uk collections: 
"Marconi' Direction Finder Type 11F, with assorted vertical and sloped ebonite panels, in a dovetailed teak case. With seven DEV/Q valves, note magnifier switch, and filaments control upon the upper vertical surface. With glazed-top radiogoniometer (scale 0-360) and tuning condenser dial (scale 0-10), parallel condenser switch, DF sense switch, upon central sloping ebonite and white plastic(?) panel. With earthing relay and calibrating choke ebonite sections upon lower vertical section. With four plugs, two nickel-plated terminals (marked "DF1", "DF2"), and a bank of five nickel-plated terminals (marked "EARTH", "PORT", "STBD.", "AFT", "FORE" respectively) on left-hand side exterior surface of the case. With a bank of five nickel-plated terminals (marked "SWITCH", "4V+", "6V+", "COMM", "HT+" respectively) upon right-hand side exterior surface of the case."

Hier finden Sie 94 Modelle, davon 92 mit Bildern und 17 mit Schaltbildern.
Alle gelisteten Radios usw. von Marconi's Wireless Telegraph Co. Ltd.