Sperry Marine, now part of the Northrop Grumman Electronic Systems sector, is based in
Charlottesville,
VA.The Sperry Marine business unit combines three well-known brand names in the marine industry: Sperry Marine, Decca and C. Plath. The original Sperry Gyroscope Company was considered a world leader in ring laser gyro systems when it was acquired by Litton Industries in 1996. This acquisition was followed by the Racal-Decca marine electronics business unit in 1997, a business with long roots in marine radar development - as Decca, it produced its first commercial marine radar in 1950. The two newly-acquired companies were combined with another Litton company, C. Plath, a Hamburg-based corporation with nearly a century of leadership in precision nautical-instrument manufacture. Thus was created a single integrated worldwide supplier of navigation, communication, information and automation systems for commercial marine and naval markets. More recently, Litton Industries was absorbed into the Northrop Grumman corporate family, although Sperry Marine continues as a recognizable entity, with headquarters in Charlottesville, VA, backed by what it claims is a worldwide network of repair, servicing and parts-distribution facilities serving every major seaport.
Today's product line from Sperry Marine comprises essentially two distinct radar types - the River Radar, and the Bridgemaster series.
River Radar:
As might be supposed from its name, the River Radar is intended principally for vessels operating on inland waterways. Specifically, it is designed to satisfy the 'Regulations Regarding the Minimum Requirements and Test Conditions for Radar Equipment Used for River Rhine and Inland Waterways Navigation', which has specialized display requirements - the radar display must operate in 'head-up' mode while in confined waters, and make full use of electronic navigation chart systems. The requirements for certification of River Radars in Europe are extensive, running to about 60 pages, and cover many aspects that might seem strange, such as specifying the controls to be available, how they operate, the language and the font-size to be used in labeling, and so on. From a parametric standpoint, they must have:
An RF of 9400 MHz, ± 40 MHz.
Pulse durations of 50/100/250 nS in short/medium/long range modes
Maximum horizontal beamwidth of 1.2°
Maximum vertical beamwidth of 30°
An antenna height of at least 5m
A scan period not greater than 2.5s,
and they must be capable of suppressing electromagnetic interference from adjacent radars, which implies complex pulse-train modulation and requires that those other marine radars have a very low duty ratio.The published characteristics of the Sperry Decca MK 6217/9 TFT River Radar, the only known model in the company's inventory, are included in Appendix 1.The physical architecture of the River Radar comprises three separate units: The scanner antenna/turning motor; a radar data processor; and an operator console.
Bridgemaster E Series
This is now the only 'high-seas' marine navigation radar produced by Sperry Marine - which is perhaps as well, since there is a dizzying range of configurations and nomenclatures for both civil and military use. Broadly, in the civil system alone, there are three levels of system capability, three display sizes, five different antenna sizes, and two basic configurations; beyond that, there is an optional processing capability, called 'Vision', which provides advanced automatic clutter suppression. The naval versions, about which little published information is available, comprise at least as many physical combinations; they may also include more-advanced target-tracking options, the capacity to fuse information from two asynchronous radars, and external synchronization with other radar systems. Finally, in their plotting options they include a 'convoy mode' allowing a convoy commander to verify the station-keeping of the vessels in the convoy. Little wonder then, that Sperry Marine closed all of its earlier product lines: its new-generation marine navigation system, the VisionMaster FT, is based on the Bridgemaster E radar, and incorporates the 'Vision' processing option as standard.This 'Vision' option exploits the cyclically-varying nature of sea and rain clutter, creating adaptive clutter-reduction 'cells' to discriminate between large cloud formations and irregular coastlines, for instance, by comparing cells with a bank of statistical clutter models. Individual cells are quite small - no more than a few beamwidths in azimuth and several pulse-lengths in range.
At the time of publishing:
There are also three variants of tracking capability - EPA, ATA and ARPA. The EPA variant is tailored for service craft and fishing vessels; the ATA and ARPA variants are intended for ocean-going vessels, the ATA variant being capable of tracking up to 40 targets and the ARPA version capable of tracking up to 60 targets. There are minor differences between the two latter variants related to automated target detection, but otherwise they are very similar.
There are two configurations: 'masthead' and 'bulkhead', defining whether the transceiver unit is integrated with the antenna or located elsewhere, such as the pilot-house or bridge.
There are three X-band antennas: 1.2, 1.8 and 2.4 m (4, 6 and 8').
There are two S-band antennas: 2.7 and 3.6 m (9 and 12').
There are two transmitter power options for X band (10 and 25 kW); and one for S band (30 kW) - magnetrons MG5473, MG5424; and either MG5223 or M1302A respectively).
The 'Vision' automated clutter-rejection facility is an option for all models.
The naval versions are described as very similar to the civil variants, with specialized plotting (such as a Convoy Mode), and external interfaces that allow the radar to be synchronized with other sensors.
There are two appendices: Appendix 1 summarizes the technical characteristics of the civil versions of the Bridgemaster E family: Appendix 2, available only by subscription, describes characteristics derived from observation and measurement of systems on the inventory of the Naval Research Laboratory.
