[Please note: the pages below are square to the screen, but the 1924 drawings are not straight on the paper and therefore appear [are] skewiff]

The very first thing which might catch your eye is that the main cavernous office had a head, a toilet, and if and when used, one was in full view of all in the office. It is one the top row of bits and bobs third from left. Generally, it was for emergency use only but that can be defined in several way. A good curry on last nights run ashore; the feeling of mal de mer coming on; breaking one's neck for a No1, and since vomiting could be classed as an emergency then so too could be a near-caught-short No2, although me thinks that only the brave would use this device!

H.M.S.HOOD was an Arrangement 'A' ship

This page tells of the main radio transmitter fitted in warships around the 1924 period.  It was called a Type 36, and as always, there were several versions of it. It was fitted into capital ships [HMS HOOD had a Type 36S to start with which was changed for a Type 36M during her last refit] and into cruisers. It was fitted into a W/T Office as shown in the pictures here, known as Arrangement A, Arrangement B and Alternative Arrangement.

This was THE W/T Office, but the ship had other offices with other less powerful transmitters.

Notice the configuration of the W/T office which is one compartment with access doors at the top {FIG 9 above}, one into the Transmitting Room [TR] and one into the Coding Office [CO].  Access to the Central Receiving Room [CRR] was via the TR. All the receivers were sited in the CRR which like the CO was manned with radio operators and Coder 'S' ratings. The power supplies for the receivers came from the batteries sited in a cupboard just outside the sound-proofed CRR, made that way so that the effect of the transmitters on the receivers would be minimal. The radio operators had to recharge the batteries often or lose power for their receivers. Note that where there was no adequate sound proofing, operators sat in either steel or wooden "SILENT CABINETS" [see Alternative Arrangement below] in FIG 11.

The TR took up approximately half of the W/T office and in all three Plans here you can clearly see that the TR was split in two: one [outside the safety cage] where men could work and which was the site of the power supplies for the Type 36 TX,  the toilet, and the trunking which took both the transmissions to, and brought the reception from, their respective upper deck aerials and deck insulators. The TX itself was sited inside a safety cage such was the potential hazard of this thermionic 'monster', and knowing what we do know about the effects of RF on our reproduction system, I fear that all these sparkers must have been sterile.


It could well surprise you to know that in the 1920's, R.N. Sparkers always referred to wavelength {λ = lambda, the 11th letter of the Greek alphabet} in metres and never to frequency in cycles.  Funny to think that since then, we have always used frequency at first in CYCLES, followed by HERTZ.  When I was a boy in the 1940's there used to be BBC radio programmes called things like "The Home Service" and "The Light Programme".  I always remember [talk about get a life} that the Light Programme was on 1500 Metres - it was printed on the wireless tuning band, and when I joined the Navy, the Light Programme was on 200 kilocycles.  Thus, I have always known how to convert Cycles [Hertz] to Metres and vice versa by using the formula [λ =speed of light frequency in kilocyles or kiloHertz]: as you know, the speed of light is a constant and is 300,000 metres per second, so knowing either the wavelength or the frequency one can work out the other unknown. For 200 kHz which is 'f' [f = 300000 1500] = 200. Other datum point to assist you are:-

FREQUENCY [f] in kHz [MHz in brackets] WAVELENGTH [λ] in Metres
1500 to 3500 [1.5 to 3.5] 200 - 85
3500 to 6000 [3.5 to 6.0] 85 - 50
6000 to 9500 [ 6.0 to 9.5] 50 - 32
9500 to 13500 [9.5 to 13.5] 32 - 22
13500 to 18000 [13.5 to 18.0] 22 - 17
18000 to 30000 [18.0 to 30.0] 17 - 10
30000 to 300000 [30 to 300] 10 - 1

I dare say that the power output of these monsters would also surprise you bearing in mind that ships in my time had an accepted maximum of 1000 Watts [1kW] although generally we achieved far less as aerial radiated power. A forward Peak Power reading of 1000 Watts was accepted as IDEAL if the VSWR [voltage standing wave ration] [the amount of power which stayed in the ship] was 0.85 or better, approximating to 850 Watts {or more} leaving the ship from the aerial.

Let me show you what is written in the Handbook for the Type 36 Transmitter namely from O.U. 5309 {OU meant "Official Use" like BR means "Book of Reference"} dated March 1924.

"The Type 36 is a high-power valve set.  It is designed to be worked off the Type 1 supply {CLICK    to see the INEFFICIENCY of the system}, and should give 5 to 7.5 kW in the aerial. {CLICK     to see the DANGERS of the UPPER DECK and the Aerials}.

 The voltages and the currents of the valves themselves are also mind blowing, with anode volts swinging from + 19800V to - 600V; with other dangerous electrical measurements on grids, in rectifiers and transformers etc. The voltages at the deck insulator was oscillating between 40,000 volts positive and 40,000 volts negative - knowing a bit about aerials, that is a tall-order to take onboard!The trunking from W/T office to upper deck which had to be vertical {the W/T office was always sited just below the upper deck or just below the armoured belt, was 4' 6" in diameter a massive hole by any standards and cut through a vulnerable area. This is a picture of the trunking    .  This trunking picture coupled with the Arrangement 'A' picture above and the siting of the trunks        

A couple of pictures showing aerial rigs for the Type 36. 


Depending upon the ship and the aerials used [and therefore the capacity of the aerial], the stated frequency range was 1000 to 5000 metres [@ 25 to 50 amps aerial current] - this is from 60 kHz to 300 kHz very much LF to MF [ Low to Medium Frequency] to us. The Type 36 could also transmit on the 600 metre band [500 kHz  {5 ton}] by adding series capacitance and a short-circuiting  link in the aerial circuit. This was the low powered section of the Type 36 which radiated on the same frequencies but at a reduced aerial current of 1.5 amps. Three emission were possible: CW [Continuous Wave or Morse Code]; ICW Double-Pulse [Interrupted Continuous Wave] and ICW Single-Pulse; those of you who remember the 600 series, will remember ICW on the 602E where ICW could only be used when the set was operating in emergency when CW, MCW and VOICE could not be used.  On the high power 60kHz to 300kHz part of the transmitter, outputs of between 3kW and 4kW could be achieved, and on the 500kHz part of the transmitter, 25 Watts was the norm.  However, the Type 36 could also transmit on HF, using the frequency band of 4.160MHz to 27MHz producing an aerial output of approximately 1kW, which is similar to HF transmitters of my day. The high powered LF/MF section was rated as being able to transmit 600 nautical miles using the main MF aerial whereas the low powered MF had a range of 25 miles. The HF side of course, given the right parameters, could communicate world wide using normal HF propagation. HMS HOOD had 2 of each of these transmitters, that is, if you like, 6 type 36 transmitters, 2 for high power MF, 2 for low power MF, 2 for 5-ton and two for HF.

As previously stated, large ships had other subordinate W/T offices housing other less powerful transmitters. Before the end of the 1920's ships had taken part in long range W/T trials and this is the cover to just one of these trials.

Then in the 1930's things began to change as modern techniques and control systems entered service.

As well as other changes, the Type 49 transmitter was introduced at the beginning of 1935 as the secondary transmitter fitted into the 2nd W/T Office of large ships, and as the primary transmitter in smaller vessels, and this time, Wavelengths [λ] had disappeared, and Frequency [kcs] was the norm. It was capable of transmitting on LF/MF [100-500 kHz]; HF [3-20 MHz]; Spark [100-500 kHz] and Low Power 100kHz-1.7MHz]. Power outputs were low to medium  in the range of 750 Watts on LF/MF and 250 Watts HF. The following pictures are of the transmitter and the associated aerials in a small ship and a large ship.




By 1939, the Type 49 had been heavily modified to allow small ships to operate it using a dipole aerial in addition to using the main MF wire roof aerial. It was also made made accurate in frequency stability, more versatile in its power requirements, given a better frequency range and more power to the aerial. Also a new add-on low power transmitter was fitted to and with the Type 49 [its name was the Type 4T]. However, perhaps the most innovative advance was the introduction of the Control Circuit Exchange, yes, the same CCX as you are familiar with. This gave the all important flexibility and versatility in allowing remote users to have various combinations of transmitters and receivers at their local positions.  The following series of pictures show the CCX, the new aerial concept [introduction of the dipole H/F Aerial], and the new transmitter 4T [the rest of the Type 49 is as shown above {2 pictures}].




Also by 1939, the highest HF [short wave] [Types 37S and 38S] frequency was 26 MHz [although most transmitters in the higher bands stopped at 20 MHz]. Above that, VHF to these men meant 75 MHz  [Type 72, 73 and 75] and only the waveguides [used to assist in the tuning of sets] went to 100 MHz.  Today of course, we use VHF for port and safety work, UHF for SATCOMS and tactical communications at sea and SHF/EHF for SATCOMS. Very little VLF/LF/MF or HF: almost the opposite to what our forebears used. Just in passing, as a professional communicator, I have a little hang-up about terminology/nomenclature! If you take another look at the last picture above, you will note that the frequency stated is 300-600Kc/s. This, as all of you will know is wrong! The word 'kilo' is ALWAYS expressed with a lower case 'k' because the upper case 'K' is ALWAYS a CONSTANT in scientific mathematical formulae - thus kilocycles should be 'kcs or kc/s' whereas kiloHertz [because Hertz is a mans name] is 'kHz'. Moving up in frequency, MegaHertz is ALWAYS an upper case 'M' and 'H', so should always be MHz, because the lower case 'm' refers to the word milli {1 1000}, therefore mW for milliWatts, Watt being a mans name.

Thus the FAMOUS 49'er was THE transmitter that all WW2 men used and knew a great deal about. Countless important messages would have been passed through its thermionic valves, each dot and dash of the Morse code being manipulated as a shifting voltage, which all helped to win the war. Destroyer/frigate/sloop/escort/minelayer/minesweeper men in their hundreds would have used this transmitter every day whilst at sea as their main transmitter, and the big boys, the cruisers, battle-cruisers, battleships and carriers would have used it on a daily basis as their secondary transmitter[s]. Artic Convoys, Atlantic Convoys, U-Boat hunters and battlegroup ships - Narvik, Crete, Sicily, Oran, Dunkirk, Normandy, River Plate, St Nazaire, Bismarck,  Scharnhorst, to mention some of them - all subjected to the influence of this 'bread-and-butter' faithful work-horse.

Before the war actually became a 'killing war', early in 1939, the Navy had seen a drawing board exercise come through all its R and D and sea environmental testing period, to become a reality. The CCX mentioned above to the Type 49, had become a CCS [Central Control W/T Systems].  The CCS was built into new ships and retrospectively fitted into older [suitable] warships. It was a revolutionary idea and broke with all that had gone before which I have outlined above, particularly in the one W/T Office with the Type 36s way back in 1924.

The CCS was an arrangement of W/T equipment in which the transmitters are grouped in one or two transmitting room, remote from, but normally controlled from, the Central Receiving Room {CRR}, in which all the main receivers are fitted.  The object of this arrangement, in conjunction with separated aerial filter units, is to reduce the interference caused by a ship's transmitters to her own reception and hence to reduce the necessity for W/T guards.  At the same time, in order to expedite the handling of messages, arrangements are made for coding and distribution of message to be carried out in one office adjacent to the CRR.  Arrangements are made also  to enable the operator at any receiver in the CRR or, with certain limitations, for any operator in any remote position, to control any transmitter. Local change-over boards and an emergency receiver are fitted in the transmitter room {TR} to enable transmission and reception to be carried out at local positions in the TR. {Ring a bell for the  600's, COMIST, MIXED FITS, ICS etc ??} Well, before I show you some more pictures, suffice to say that the war did become the 'killing war' with, for us in the R.N., the loss of HMS Royal Oak at Scapa Flow/loss of life in our brave cruisers engaging the Graf Spee in the River Plate, and very soon, the money we had [and that borrowed in large quantities] went towards building new ships.  As long as these new ships could send and receive a message whilst at sea, then to hell with all the fancy ideas for the time being. Hundreds of smaller ships [destroyers, frigates, sloops, escorts etc] were built and made ready for service, and when the war was over, the navy had a glut of these ships [thankfully - they were not sunk] all with their less than adequate technology, including W/T office equipment and layouts. Like so many of you, my first ship, a Castle Class frigate cum sloop {HMS Tintagel Castle] had but one office with everything in it {87M, TypeX/CCM, FM12, TBS, 89Q, 60EQR, TCS, 691H/CUH, B28's B29's and a B40], and that can be repeated with many other classes of ship pre-war, war years and post-war built.

This is the nomenclature for CCS      and this is the overall diagram of the system   {click here for a quick description of the transmitters in    each of the two TR's}.  Now for pictures of the CSS -       

First the central control [switch] panel sited in the CRR or CCO       then the controller for TR1 and three of its four highest powered transmitters      followed by the controller     for TR2 and its transmitters.   


This little piece of kit is the transmitter control panel giving control of any transmitter to any of the eight CRR or CCO bays/operators                                                              
                     whilst this piece of kit is the telephone patch board for the internal communications


If you now look back to the First picture, the central control [switch] panel, you will see that the last four pictures are an integral part of the central control panel.  This system, I am sure, gave the idea to ASWE [Admiralty Surface Weapons Establishment] to develop ICS [Integrated Communication System] of which we are all more than familiar with. Today, in April 2005, the Navy is using ICS10.  ICS1 was on the drawing board in the late 1950's and at sea in the early to mid 1960's. In my time {I left in June 1983} ICS2 was the norm with ICS1 being phased out, and with ICS3 in its build mode ready for full trials.

That is it - just a quick look down memory lane for us ex communicators.  I hope that you enjoyed the page. Best regards.