decca_globe.gif The Decca Navigator System, herein abbreviated as DNS for convenience, is a hyperbolic radio navigation system which was established in the United Kingdom after World War 2 and later used in many areas around the world. It operated by measuring the phase differences between continuous signals from a master and slave stations. These differences were then related to a hyperbolic lines printed on a chart. By plotting the readings from two pairs of hyperbolas at any particular instant, users could plot their position instantly.

The system used groups of at least three shore based transmitter stations called chains operating in the 70-130 kHz radio band. Each chain comprised of one Master and two or three Slave stations, usually located 80 to 110 km from the Master station. The accuracy of DNS ranged from 50 meters during daytime to 200 meters at night. It could decrease up to 800 meters as the distance from the baseline increased. Accuracy was also affected by seasonal effects which generally reduced the accuracy by a factor of 6 to 8. The maxium daytime range for DNS was 300 to 400 miles with a reproducibility of 200 meters. At night, accuracy was guranteed out to 240 nm by the British Admiralty.

For a comprehensive look at Decca, select the following:
Decca Archive (IET off site link) 
Corporate Highlights
System Overview
Transmitters and Antenna
Description of Chains
Decca Survey Chains
Receivers and Indicators - Airborne Types
Receivers and Indicators - Marine Types
Test Equipment 
Manufacturing Facilities
Sales Demonstration Aids
Decca  Hyperfix  
Key People
Decca Memorabilia
Decca Navigator News Listing 
User Comments and RCN Useage
Submissions From Former Employees
Looking For Former Employees
Museums and Collections 
Wish List for HMCS HAIDA

This was the corporate logo of The Decca Navigator Company as imprinted on a system manual. (Graphic courtesy The Decca Navigator Company)

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