In the earliest of days of W/T in the Royal Navy (documented under the 19th century files 1895-1899 and the early 20th century files 1900-1913) ships were fitted with W/T adhoc. Whether fitted with Marconi gear or Captain Jackson's Service gear, the bits and pieces were put together with the sole aim of transmitting and receiving on a single wavelength only. Wavelengths, and to start with there were very few, were called 'TUNES'. Thus ships were allocated to given wavelengths and the experiments (aerial coupling, transmitter and receiver refinements etc) took place on the one and only wavelength possible along with operational use. The early Tunes were called 'A' 'B' and 'C'. The apparatus fitted to achieve such communications were mounted on large sheets of copper which were screwed to the bulkhead of the W/T office, and some of these pieces could be changed by the operator to assist in the correct tuning of the apparatus. It was often an electrically dangerous environment and none of the apparatus was boxed. Mutual interference was a problem as was noise. The tiny received signals from the early coherers (and then crystals) meant that they were difficult to read. To assist the operator, Silent Cabinets were invented and these were sound proofed. They were sited in the W/T office. The operator of the watch would sit inside the Cabinet (with his Morse key and his receiving equipment) where free from noise, he could read and transcribe incoming messages and send outgoing messages to the aerial.

  Tune 'C' later differed from Tunes 'A' and 'B' because it became a type of apparatus (as opposed to a single frequency/wavelength facility) and could transmit on other wavelengths too, specifically on 'S' 'T' and 'U' Tunes and achieved greater ranges than did the system which followed it namely the Service Mk I Set. 'C' Tune expanded and became 'C Tune Mark I' and then 'C Tune Mark II'.

  As time went on and W/T techniques were proven by experimentation, more and more Tunes became available and some ships could transmit on more than one frequency simultaneously.

  However, as you will read (and as the chart above clearly shows), the vast majority were in long wavelengths with only a handful in the short wavelengths, stretching from the upper frequency limits of the VLF band (30kHz), through the entire LF and MF bands and into the lower reaches of the HF band with approximately 2.5MHz as the upper limit. In the very earliest of days the ionosphere was not known about although they did appreciate that signals travelled further distances by night than they did during the day.