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THE POST WW1 YEARSThe 1920s
© RN Communications Branch Museum/Library |
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The period 1918 onwards until the early 1920's (approximately 1922-3) saw many improvements and much innovation but much of it was in command/control of the W/T environment both for the operators and for the remote users of wireless facilities/circuits.. Spark and Arc transmitters were still widely fitted alongside an increasing number of valve sets and the chief way of communicating was still with Morse code, whether by damped waves (Spark) , CW (Arc and Valve) or ICW (Valve). In many ways, receivers had progressed faster than had transmitters, and by this time, the norm was a receiver with valves and heterodyning was common practice for the detector stages. When (and in the mid 20's) the heterodyning process was first applied to RN receivers to create a fixed frequency signal processing stage, it was called supersonic (because it was above AF range and thus RF still) and in the 1931 "Notes of W/T Sets" (BR222), it was described thus:-
"The following names have been agreed upon by international convention for the frequency bands specified.The following block diagram might have been used for instructional purposes in 1930* Page 353 Chapter XIV - Remember, the theory is sound and well understood but the application is not yet mastered!By "Radio-Telephony" [R/T] is meant direct communications by speech by wireless methods, whereas "wireless telegraphy" indicates the use of Morse code. For Service purposes, R/T possesses special advantages over W/T in cases where high speed of communication and very rapid fulfilment or orders given is desired. In cases where a message must be written down, R/T is not appreciably quicker than W/T when plain language is transmitted as W/T messages can be sent and received at a rate limited only by the speed at which the message can be written down. The use of R/T is at present undeveloped, and a great number of problems remain to be solved, but there is no doubt that its range of utility for Service and commercial purposes will be very wide." By the time the 1931 edition of the Admiralty Handbook of Wireless Telegraphy * had been published [which superseded the 1925 edition] R/T was being described as:-* Page 675 Chapter XV"Radio Telephone R/T consists in the transmission of speech, music or any audible sound to a distance by means of electro-magnetic waves. It bears the same relation to wireless telegraphy as line telephony does to line telegraphy, and possesses the same relative advantages and disadvantages. More particularly with reference to Service requirements these may be summarised as follows:- Advantages a. All the normal advantages of oral over written communication e.g., actual saving in time, and the lessening in traffic that arises by the adjustment of the interference caused by R/T is worse than that caused by W/T. Conversely, interference exerts greater influence on a receiver adjusted for R/T minor points without the necessity of voluminous correspondence. The ability to make and read Morse is not required. Disadvantages a. Where a message has to be written down, R/T is slower than W/T b. Coded messages are difficult to pass owing to risk of phonetic errors, and plain language involves the risk of interception. c. The interference caused by R/T is worse than that caused by W/T. Conversely, interference exerts greater influence on a receiver adjusted for R/T than on one adjusted for W/T, and, in addition, the effect of any interference heard is of more serious consequence. d. Listening-through is not possible with R/T unless the "single side-band" system is employed. However, the 1920's, used for many experiments, did see the end years of that decade with an efficient R/T system although once again, used mainly at the V/HF frequencies and not for MF or HF working: these continued to be used for CW and ICW only. What follows is the NSR [Naval Staff Requirement] for W/T General dated January 1938. There are several items within of interest. We have talked much about SPARK transmitters [see the PRE WW1 files] and its broadband emission causing considerable interference to nearby shipping. In paragraph 9 of this NSR we read that as from 1936 - SDO 285/36 - a Spark transmitter is fitted PURELY FOR DELIBERATE JAMMING OR ANTI-JAMMING USE. Paragraph 12 of the NSR confirms that even as late as 1938, only a FEW SHIPS had a requirement for R/T and these did not include Capital ships other than aircraft carriers. Note in Section A [Capital Ships] that the short distance set has moved away from the lower end of the HF band to upper end of the HF band/lower end of the V.HF band i.e., to 30 to 60MHz. Also in Section A, the Fire Control set frequency has moved up to V.HF which was also supplemented by the Spotting Top Aldis Lamp keyed remotely from the TS of the gun turret concerned.WT NSR 1938In the first paragraph above I mentioned the great improvements in the wireless telegraphy environment. This involved power supplies, wiring/cabling in general, aerial and send/receive change over systems, office layouts and the remote user who in the early days, particularly of R/T, had to come to the wireless office to use the 'system microphone'. This period said good bye to the long standing Silent Cabinet in which sat the receiving operator who also sent the Morse code outgoing messages. All major ships were either built with or modified to have, a new suite of three offices:- For TRANSMITTING were called: a. The Main Office which was also called No1 TR [transmitter room], b. The Second Office or No2 TR and c. The Auxiliary Office. For RECEIVING they were called: a. The CRR {central receiving room which took over from the Silent Cabinet], a. Second Office and a. The Auxiliary Office. In smaller ships [Flotilla Leaders and Destroyers] they had three offices also but their names were slightly different to those of larger ships. Equipment generally came as packaged items instead of the piece-meal assemblies [many of them self-build] of yore. Mind you, this often resulted in complicated apparatus [the Type 35S is a good example] and certainly the resultant equipment was on the large side. Before we leave this period let us briefly look back to summaries the Royal Naval W/T transmitters from the very beginning. We have now seen the four unique methods of transmitting W/T signals from the earliest of times right through the period leading up to the 1930's and because one of the methods discussed is a valve transmitter, right up to the end of the thermionic age! In the 19th Century files and in the PRE WW1 files we have talked a great deal about the SPARK, the ARC and the HF Alternator methods and mention has been made here on this page and also in the earlier timed pages of valves. Now we can summaries these methods by highlighting their advantages and disadvantages vis-a-vis one another. Methods:- a. The SPARK system = Damped Waves. b. The ARC system = Undamped or Continuous Waves. c. The Valve system = Damped or Undamped Waves at will. d. The HF Alternator system = As for [b] above, but this method is not relevant to the Royal Navy. |