This post will be about the Naval Tactical Data System, or NTDS.
NTDS as a concept is nearly 50 years old. The system transmits radar symbology among the ships in a task group. The original computers had a whopping 32Kb of core memory and they took up huge equipment spaces. They probably cost well over $500,000 in a day when an expensive new car cost $3,000.
In the `70s and `80s, the computers were replaced by AN/UYK-7s, computers that required air-conditioned spaces, water cooling of the equipment cabinets, special technicians to maintain them and were less capable than today's $500 desktop computer.
NTDS transmitted via radio (primarily UHF, I think) on three different data streams: Link 11, Link 14 and Link 4A.
NTDS enabled all ships in the task group to share contact and target data without voice comms.
Link 11 was a full two-way datalink. Link 11 ships both could originate the symbology and display it. The symbology was displayed on specially-equipped radar scope head. The symbols were a diamond shape (hostile), square (unknown) and circle (friendly). Full shapes were displayed for surface contacts, the upper half of the symbol was displayed for air contacts, the bottom half for subsurface contacts. Directional arrows were added, with varying lengths to give a graphic indication of speed. There was a numeric designation and additional data (course, speed, altitude or depth).
A Link 11 ship could be radar quiet, but because it was receiving Link 11 telemetry, all of this was displayed on the ship's NTDS scopes in CIC. The computers on each ship displayed things so that if no offset was selected, the display centered on the ship.
Aircraft carriers, cruisers, E-1/2s and long-range AAW shooters had Link 11 (CG-16/26, the few nuke cruisers, DDG-37s). Short-range AAW shooters (DDG-2s, FFG-1s) and ASW frigates generally had Link 14. Link 14 was not a computer link; the data was converted into teletype symbology. Sailors on Link 14 ships had to read the teletype data to other sailors standing behind transparent vertical plotting boards, just as they did in World War II. In a hot environment, Link 14 data was several minutes old by the time it was plotted and, for the purposes of AAW, it was all but useless.
Link 4A was a one-way datalink to older fighters, such as F-4s and F-8s. The symbology showed on their radar screens, enabling the controllers to designate targets to those aircraft without speaking over the voice link.
The F-14s' AWG-9 radar, while not capable of 360 degree coverage like the E-2, had a capability of detecting targets at long range. F-14s could and sometimes were used in a radar picket role; they were the first fighters equipped with Link 11.
Once things went really hot, then the voice comms came into use. That'll be the next topic in this series.
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