The history of the development of equipment for Decca Navigator stations has been a continued search to establish the high quality, reliability and continuity of service so vital to the confidence of the user of such an important aid to navigation. The programme has called for constant and careful design judgment to assess the overall benefits of introducing promising new technology as against relying on well established techniques of proven performance.

Thus the general trend has been the introduction of a series of well tested though sometimes minor developments over an extended period. These improvements have been followed by major developments when new technology has clearly reached a point where it can be used with confidence to provide new and important facilities which operational requirements can justify. The policy has led to a number of distinct generations of equipment, each incorporating a progression of improvements as development continues. Such a new generation in the development of Decca Navigator was initiated as a result of requirements for the Norwegian chains which arose in the early 1960's. The terrain and climatic conditions in that country emphasized, for the first time the need to develop an unmanned system capable of deployment in remote areas of Norway, whilst at the same time providing full performance and continuity of service under the most adverse conditions.

This generation became known as the 1880 Series. Initially it was aimed particularly at completely unmanned operation for long periods. More recently, as will be described later, other versions of the series have been designed. These versions provide various levels of control and facility to plan cost effective solutions to a number of operational requirements needing differing degrees of manning and remote operation.

The 1880 Series development programme, spread over the last ten years, has introduced other major improvements and additional facilities ensuring that Decca Navigator Stations are kept abreast of modern technology and provide the highest possible standards of quality and reliability.

The most significant development of the 1880 Series was the provision of remote monitoring and control facilities needed for unmanned operation in remote areas where terrain and climate make access uncertain. The essential characteristics of the Decca Navigator transmission format are complex in timing and phasing. Considerable design ingenuity has permitted the transmission of additional remote monitoring and control signals within the overall transmission modulation cycle in such a way as to ensure no adverse effects on the quality or reliability of the main navigation service whilst at the same time avoiding the expense of a separate radio link.

Another important development was the replacing of all mechanical relays with solid-state devices. This has provided the expected reduction in the effort and cost of maintenance and improvement in reliability.

There have been progressive developments to replace thermionic valves with solid-state circuits wherever improved performance can be established. A few valves are however still retained in circuits where they have proved extremely reliable. A full solid state design is now proceeding in a form which can be incorporated in new 1880 equipment and will permit retrospective modification of existing equipment if required.

The 1880 development included full recording facilities to assist fault analysis and thereby contribute to the efficient operation of the stations. This fault analysis capability provides an important indication of the most beneficial line for future development, thus assisting in the progressive long term improvement of station equipment design.

,The 1880 System incorporates a modular design to facilitate permutation of main units in order to fulfill a range of possible requirements. In general, this has led to a simplification of the servicing procedures and to a rationalization and consequent reduction of the essential spares needed.

These progressive developments in the 1880 Series now allow us to offer four distinct levels of technical facility, all aimed to provide the basic navigation service, and with a number of additional optional features, depending on the particular requirement.

The Full 1880 System

This provides the total range of the available facilities including unmanned operation of stations, full redundancy, continuity of service of a very high order, and recording and fault analysis. This full system is aimed to give a comprehensive service to satisfy the most demanding operational requirement.

The 1880 Triplex System

This is the next level of equipment available. It is not so comprehensive as the full system, but provides triple redundancy of main equipment thus retaining a high order of continuity of service. In order to allow a significant reduction in cost compared with the full system, features which do not contribute to this basic navigation facility such as, for example, auto-changeover circuits and recording and fault analysis are not included in this system.

The 1880 Duplex System

In this version of the 1880 Series, the facility has been designed to reduce still further the cost of the system whilst retaining the essential performance and a reasonable level of continuity of service, This is made possible by providing main and standby equipment for all main units so that one faulty unit in any main equipment area will not affect the overall serviceability of the navigation facility.

The 1880 Simplex System

This Simplex System comprises a basic Master and three Slave Systems with no equipment redundancy and no 'frills',

This, the simplest and least expensive of the 1880 Series, is aimed to meet requirements where it is desired to provide a full navigation service; breaks in that service can be accepted provided they are known and cannot result in false information being radiated.

Each of the main system configurations described can be provided in a form most suitable for either fully manned or partially manned Chain operation, depending on specific customer requirements. In the Simplex, Duplex and Triplex versions, the control in the partially manned cases can be provided in a number of ways but a most cost effective manner is by the use of Decca Centralized Control and Switching System (CC/SS) which permits an operating engineer at the Master Station to control the equipment at all three Slave Stations. A particularly elegant design combines both 1880 and CC/SS as an integrated equipment package.

Another important feature of the 1880 Series is the modular design of the main items so that all versions are composed of common units. This allows considerable g flexibility to meet individual customers' is technical and budgetary requirements. It also gives advantages in maintenance, spares holdings and in training. Further, it allows a customer to extend his facility in a rational and cost effective manner if his operational requirement becomes more demanding.

It will be clear from what has been said that 1880 Series equipment provides a wide range of options designed to meet all likely operational requirements in the most cost effective manner. The series is in already deployed in many countries and is fully proven in operation as an accurate and reliable equipment. Important extensions of Decca Navigator coverage are already planned and others are being negotiated, based on this 1880 Series of equipment, which will add considerably to the extensive world coverage already provided by Decca.

Duplex Phase Control cabinet for slave station

Duplex Phase Control Cabinet - interior

Monitor recorder 920/Z and monitor receiver model 1883.

Transmitter room.

Master station control room.

Slave control type 1880 . The master cabinet is generally similar.

All photos in this table from Decca Navigator News , December 1973

 

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