Communicating to and between ships at sea has always been a key need for shore and sea-going commanders. Its importance cannot be underestimated. Nelson at Trafalgar gained some of his superiority because he had a good signal codebook produce by Admiral Popham some 10 years earlier and was able to transmit sophisticated manoeuvring signals to his captains. Furthermore the receiver system (the telescope), invented 200 years previously, had undergone spiral development and the object lenses then available meant that there was good colour discrimination, reducing the error rate in reading the flags. This enabled Nelson confidently to exploit the tactical situation as well as allowing him the luxury of sending morale-raising messages: ‘England expects . . ‘ etc.
Interestingly, where traditionally technology such as optics was developed over many centuries led by the military need, today, driven by a booming telecommunications and IT industry, the rate of change of communications technologies lasts, at best, for 10 years or less, and the engine for change is not military need.
Ship to ship communications improved as semaphore and light transmitted Morse code were developed. These had the added benefit of confirmation that the recipient had received the message, and of course a greater volume of data could be sent. (The downside was that the tradition of pre-battle dinners given by admirals to discuss and agree strategy quickly waned, possibly to the benefit of their livers).
Radio communication, initially HF, was the great liberator. Everyone could talk to everyone – provided, of course, that the ionosphere was not being too difficult with sunspot activity, that the correct frequency had been calculated to give the right ‘skip distances’ round the world, and that aerials were working. This brought individual ship captains closer to their command chain, though they lost a little of their independence. No longer would reports take months to reach the Admiralty. Submarines remained private for a little longer but as fleet vessels their need for good communications is the same as any other warship.
Embracing radio started an avalanche of communication requirements. A simple example is supporting the Army for doing shore bombardment. To ensure communications either a naval party was put ashore with naval radios, or the Royal Signals went to sea. Inconceivable these days. Interoperability is now a must, though shore bombardment remains on the menu of naval services. Consider how the problem is magnified many times for targeting TLAMs. Then consider the issues for initiating a Trident missile firing.
So, a 21st century naval vessel has to talk to other surface and subsurface naval vessels close to it, and have secure, reliable communications with the HQ ashore. It must talk to aircraft, receive and contribute to worldwide intelligence, and receive administrative emails. No sailor these days is happy to be far from personal access to the internet. Thus a modern warship needs communication systems covering the whole frequency spectrum from VLF to talk to submarines, to the very high frequencies required to talk to satellites. Each has its own transmitter and a receiver path; each has a crypto and a printer and screen for the operator. There is a veritable snake’s honeymoon of signal paths within the ship. The external forest of aerials too needs careful management to ensure no mutual interference within the communications systems, or the radars, or the ESM equipment, or the recreational TV aerial.