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 DEPARTMENT OF SCIENTIFIC AND INDUSTRIAL 
 RESEARCH. 
 
 , Brvt . 
 
 RADIO RESEARCH BOARD. 
 
 SUB-COMMITTEE ON RADIO TELEPHONY. 
 
 REPORT. 
 
 Presented to Parliament by Command of His Majesty. 
 
 LONDON: 
 PUBLISHED BY HIS MAJESTY'S STATIONERY OFFICE. 
 
 To be purchased through any Bookseller or directly from 
 H.M. STATIONERY OFFICE at the following addresses : 
 
 IMPERIAL HOFSK, KINOSWAY, LONDON, W.C. 2, and 28, AHINGDON STREET, LONDOW, S.W.I; 
 
 3,, PETER STREET, MANCHESTER; i, ST. ANDREW'S CRESCENT, CARDIFF; 
 
 23, FORTH STREET, EDINBURGH 
 
 1922. 
 . 1707 Price 3d. Net.
 
 RADIO RESEARCH BOARD, 
 
 SUB -COMMITTEE E. (RADIO TELEPHONY). 
 
 Admiral of the Fleet Sir HENRY B. JACKSON, G.C.B., K.C.V.O. 
 
 F.R.S., M.I.E.E. (Chairman). 
 Professor C. L. FORTESCUE, O.B.E., M.A. ; M.I.E.E. 
 Professor G. W. 0. HOWE, D.Sc., M.I.E.E. 
 Major A. G. LEE, M.C., B.Sc., A.M.I.E.E. 
 
 Secretary: Mr. 0. F. BROWN, M.A., B.Sc. 
 
 NOTE. Major A. G. Lee (General Post Office) had to proceed 
 to India in connexion with the Imperial Wireless Chain during 
 a part of the time that the Committee was sitting, and his place 
 was taken during his absence by Mr. E. H. Shaughnessy, O.B.E., 
 the Post Office representative on the Radio Research Board. 
 
 We were appointed by the Radio Research Board on the 
 4th October 1921, as a result of the following resolution of the 
 Imperial Conference : 
 
 " That the Radio Research Board be asked to investigate 
 the subject of Wireless Telephony and to report on its 
 development whether governmental or private. 
 
 " That the Postmaster General shall supply to the 
 Governments of the Dominions and India technical reports 
 showing its position and possibilities." 
 
 We have held eight meetings and have completed our examina- 
 tion of the present position of Radio Telephony in this country. 
 In this work we have been assisted by witnesses from the three 
 Fighting Services, and from Marconi's Wireless Telegraph 
 Company, Ltd., and the Radio Communication Companv, Ltd., 
 the following gentlemen giving evidence : 
 Major J. R. ERSKINE MURRAY, D.Sc. (Air Force) (Instrument 
 
 Design Establishment). 
 Lieutenant-Colonel A. G. T. CTJSINS, C.M.G., R.E. (Army) (Signals 
 
 Experimental Establishment). 
 
 Mr. C. A. IRVING (Navy) (H.M. Signal School, Portsmouth). 
 Mr. G, S. FRANKLIN (Marconi Company). 
 Captain H. J. ROUND, M.C. (Marconi Company). 
 Captain N. C. LEA (Radio Communication Company).
 
 \ K, 
 
 (,550 
 
 We have the honour to submit the following report. 
 
 1 . Relative merits of Wireless Telegraphy and Radio Telephony. 
 All the witnesses we have examined agree that for the trans- 
 mission of a specific message over any distance long or short 
 the Radio Telephone is greatly inferior to the Radio Telegraph 
 in accuracy, speed, and cost ; and is likely to remain so. The 
 witnesses agreed that the articulation of the best Radio Telephone 
 installations known to them compares favourably with that over 
 a trunk land line, but all agreed that it is necessary to repeat or 
 spell unusual words or proper names and repeat figures. Our 
 witnesses agreed also that the skilled personnel necessary to 
 work a large Radio Telephone installation or a number of small 
 ones is approximately that necessary to maintain similar Radio 
 Telegraphy stations. 
 
 We consider, therefore, that the spheres of utility of the two 
 systems are as separate and clearly defined as those of land line 
 Telephony and Telegraphy. 
 
 2. Possible applications of Radio Telephony. With land line 
 Telephony there are local connexions often many thousands in 
 one locality and trunk lines. Considerations of mutual inter- 
 ference quite irrespective of the greater convenience of land lines 
 rule out the Radio Telephone for local connexions. We consider 
 therefore, that the most important applications of the Radio 
 Telephone on a commercial scale are as connecting links between 
 ordinary land line telephone systems either at great distances 
 (e.g., between Europe and America), or at medium or short 
 distances between islands; or as a means of communication 
 with isolated posts, lightships, etc., where the laying of a telephone 
 cable would be expensive or impracticable; or possibly as short 
 links in land trunks across swamps or virgin forests where land 
 lines are difficult to maintain ; or again, broadcasting intelligence 
 and music for the general benefit of the community is a further 
 example of its commercial utility. 
 
 There are occasions, also, usually in the case of very short 
 distances, when personal communication between Principals is 
 essential and secrecy is unimportant. In these cases the use of 
 a Radio Telephone, even independent of land line systems, may 
 be very convenient. The Fighting Services have directed their 
 development of Radio Telephony almost entirely to meet such 
 demands, and have developed efficient non-secret installations 
 suitable for their special requirements. For example, the Air 
 Force make use of Radio Telephony daily in the navigation and 
 landing of aircraft ; and it has been developed to a certain extent 
 in the Navy for communication between particular officers of 
 ships in close company. The need for similar communication 
 may also arise commercially. For example, when a ship is 
 approaching harbour, direct communication between the Master 
 and the Port Authorities with regard to berthing and other 
 matters might effect a considerable saving of time in getting 
 alongside. 
 
 X (87)18152 Wt 91 OS G 251 1500 7/22 
 
 283289
 
 3. Requirements for a Commercial Service. The requirements 
 of any system of telephony for commercial success may be 
 summarised as follows : 
 
 (a) The articulation must be reasonably good. 
 (6) It must be possible for subscribers to be connected 
 either during the whole day or during specified periods 
 without excessive delay. 
 
 (c) The running and maintenance costs must be such 
 that without excessive charges the Service can pay its 
 way. 
 
 (d) Some degree of secrecy must be provided. 
 
 For successful operation, a Radio Telephone installation must 
 satisfy these requirements to the same extent as a land line 
 system. With regard to (a) the Radio Telephone must give at 
 least as good articulation as existing land lines give. To satisfy 
 (6) sufficient power must be used to overcome all interference 
 from other signalling or from atmospherics during the whole 
 24 hours (or, where a limited service is all that is required, during 
 such hours as the service is open to the public). But in order 
 to comply with (c) this power must not be so large that running 
 and maintenance costs are excessive. The interference of atmo- 
 spherics is very variable both in respect of locality and season, 
 and in certain localities communications may be interrupted 
 from this cause for hours or days, even when very high trans- 
 mitting powers are used. As regards (d) the ideal, of course, is 
 absolute secrecy ; but a service might be considered commercially 
 possible if the interception of a conversation required costly and 
 elaborate apparatus needing skilled adjustment, thereby making 
 interception a matter of great difficulty and impossible with 
 ordinary radio telegraph receiving instruments. 
 
 Furthermore, where the Radio Telephone is a link between 
 land line systems it must provide for direct connexion to these 
 systems so that two subscribers may be able to communicate 
 from the telephone installations in their own homes or offices 
 without having to travel to special radio stations to carry on 
 their conversation. 
 
 4. Grouping of the Evidence. The evidence we have collected 
 as to the feasibility of Radio Telephonic Communication divides 
 itself into three parts evidence on the practicability of commu- 
 nication over (a) long distances of the order of 3,000 miles or 
 more, (b) medium distances of the order of, say, 1,000 miles, 
 (c) short distances of the order, of 200 miles. 
 
 5. Long Distance Radio Telephony. With regard to long dis- 
 tances it appears that, under those favourable conditions which 
 are experienced for a few hours daily in most places, it is tech- 
 nically possible for speech to be transmitted through the ether 
 to any range up to the distances which are now judged feasible 
 for reasonable Radio Telegraph communication. Thus, given 
 two radio installations of sufficient power, a person could carry
 
 on a conversation with another person at these distances pro- 
 vided expense was no object and secrecy was immaterial. 
 Demonstrations have been given, and will probably continue to 
 be given, of the transfer of speech by non-secret methods over 
 distances up to 2,000 miles or more 1 . We believe, however, that 
 no organised experimental work with a view to providing a 
 reasonably secret commercial service over such distances is 
 being carried on or is contemplated either by Government 
 establishments or by commercial firms in this country. We 
 consider that the possibility o establishing satisfactory radio 
 telephone communication on a commercial basis over a distance 
 of 3,000 miles or more is remote. 
 
 6. Difficulties of Long Distance Radio Telephony. The reasons 
 for this conclusion may be stated as follows : 
 
 (a) The wave lengths most suitable for long-distance 
 Radio Telegraphy are unsuitable with the methods at 
 present in use for Radio Telephony, and telephonic com- 
 munication would therefore have to take place on wave- 
 lengths which are known to be inefficient for long ranges. 
 
 (6) The power required for Radio Telegraphic commu 
 nication for a 24-hour service daily is already very large, 
 and in spite of the improvement in receiving apparatus 
 modern practice favours the use of higher powers for long 
 distance communications than were considered adequate 
 a few years ago. 
 
 In consequence of (a) and (6) above, witnesses variously 
 estimated the powers for Radio Telephone services to be from 
 3 to 20 times greater than those at present considered necessary 
 for similar Radio Telegraph services over the same ranges. The 
 necessary charge for a conversation would accordingly reach an 
 impracticable figure. 
 
 (c) No means at present are known by which any 
 appreciable secrecy can be obtained for a conversation 
 taking place at such a range. That is to say, the conver- 
 sation can be picked up at any Radio Telegraph Station 
 or by any amateur within range, having receiving instru- 
 ments which can be tuned to the wave length used. (See 
 also last sentence of paragraph 9 (d).) 
 
 (d) The interference with other radio communications 
 would be greater than that due to two Radio Telegraph 
 stations communicating over the same distance on the 
 continuous wave system, owing largely to the increased 
 power. 
 
 (e) Radio Telephone communication would be exposed 
 to atmospheric interference, and the interference of other 
 radio stations, to a greater extent than Radio Telegraph 
 communication over the same distance. With a long dis- 
 tance Radio Telegraphic service it is possible in the event 
 of temporary adverse conditions to hold back traffic for
 
 half an hour or an hour without serious results, but with a 
 number of subscribers waiting to use a long distance Radio 
 Telephone, a delay through any disturbance would be most 
 detrimental to the service. 
 
 7. Medium Distance Radio Telephony. For medium ranges, 
 we consider that the difficulties as regards a commercial service 
 are practically the same as those for long distances, except for the 
 fact that unless considerations of mutual interference prevailed, 
 the waves which could be used for Radio Telephony would be the 
 same as those which are efficiently used for Radio Telegraphy. 
 We consider, however, that in remote localities where the danger 
 of mutual interference between Radio stations is small and the 
 risk of interception of the conversations by unauthorised persons 
 is slight either because of the sparseness of population or for 
 other reasons a Radio Telephone service employing waves of 
 the length used by medium power Radio Telegraphy stations 
 would be possible; provided, always, that the cost of the 
 necessary additional power was not prohibitive. As in the 
 case of the longer distances we believe that no organised experi- 
 mental work with a view to providing a reasonably secret 
 commercial service is being carried out. 
 
 8. Radio Telephony over Short Distances. The position as 
 regards short distance communications is, however, more hopeful. 
 We have learnt that the Marconi Company in this country is 
 experimenting with semi-secret systems with the expectation of 
 placing Radio Telephony on a commercial basis in the near 
 future for distances up to about 200 miles over sea. The repre- 
 sentatives of the Marconi Company have kindly furnished us 
 with a complete description of the installations intended for 
 such a service between this country and the Continent, using 
 short wave lengths of the order of 100 metres and a power of 
 5 K.W. This Company has informed us also of the very pro- 
 mising results of certain experiments carried out by their experts 
 at a range of 90 miles over land using wave lengths of the order 
 of 20 metres. Although this latter line of development appears 
 promising, it must be recognised that the system proposed is 
 only in the experimental stage. Neither of the systems has yet 
 been tested in an actual commercial service. 
 
 9. Extent of the Success of Short Distance Radio Telephony. 
 We consider that the conditions requisite for a commercial 
 service as enumerated in paragraph 3 of this report, can be met 
 at the present time in the case of a service over a short range to 
 the following extent : 
 
 (a) The articulation is approximately as good as on 
 land lines of similar length. 
 
 (6) It seems probable that a full 24-hour service could 
 be maintained in most localities. 
 
 (c) Atmospheric disturbances and, under present con- 
 ditions, interference by and with other stations are very
 
 much less troublesome on the short waves used, so that 
 delays of traffic through these causes are less probable, and 
 the power required is not excessive. 
 
 (d) Unauthorised reception is made more difficult by 
 the use of short waves, but the conversations can be picked 
 up by special apparatus. In the case of very short waves, 
 instruments of very special design are required; and, 
 moreover, the transmission can be made to some extent 
 directive, i.e., the waves can be made stronger at points 
 on the line joining the- transmitter and receiver than at 
 points off that line, thus reducing the area over which 
 interception is possible. In any system, irrespective of 
 distance, the use of different wave lengths for transmission 
 and reception at a given station makes it more difficult for 
 one person to overhear the whole of a conversation. 
 
 (e) There are no insuperable difficulties in the system 
 being worked satisfactorily in connexion with the ordinary 
 trunk lines, and, as far as subscribers are concerned, the 
 conversation can take place exactly as with the land line 
 system, i.e., the subscriber has not to instal in his office 
 any special apparatus or to manipulate any switches 
 during a conversation. 
 
 10. Note on the Use of very Short Waves. It will be noticed 
 that the solution of the practical difficulties of commercial appli- 
 cation of Radio Telephony outlined above depends largely on 
 the use of short waves. The system is thus limited to compara- 
 tively short ranges, and the achievements of this line of develop- 
 ment cannot be extended to Radio Telephonic communication at 
 longer distances without resorting to longer wave lengths with 
 the consequent elimination of the slight degree of secrecy the 
 use of short waves at present gives. 
 
 It should be noticed also that the absence of interference 
 on short waves is mainly due to the fact that these wave lengths 
 are not greatly used at present for radio communication. The 
 increased use of such wave lengths by a number of Radio Telephone 
 services would probably cause mutual interference to nearly 
 the same extent as is now experienced on longer wave lengths. 
 
 11. Summary of Conclusions. The conclusions of this report 
 may be summarised as follows : 
 
 () We consider that the development of Radio Tele- 
 phony for long ranges is in an extremely elementary stage, 
 and we see no line of development which would be likely 
 to lead to its establishment on a commercial basis within 
 a measurable period. 
 
 (6) For ranges of the order of 1,000 miles, we consider 
 that in certain remote localities, where the interference 
 from atmospherics and other radio communications is not 
 excessive, it would be possible to establish non-secret 
 Radio Telephonic services using waves of the length usually 
 employed by medium power Radio Telegraph stations 
 
 280239
 
 communicating over the same range. The power necessary 
 for Radio Telephony, however, would be much greater 
 than that required for satisfactory communication by 
 Radio Telegraphy over the same distance. 
 
 (c) For ranges of the order of 200 miles, we consider 
 the position more hopeful, and it seems that the lines of 
 experiment which are being followed will lead to the 
 development in a reasonable time of a system of Radio 
 Telephony which will approach approximately at any rate 
 to the requirements of a commercial system. 
 
 (d) We cannot, however, recommend the use of radio 
 telephony as a substitute for any other means of telegraphic 
 communication except in those"" cases where the special 
 requirements can be met in no other economic way; for 
 example, the broadcasting of intelligence of general infor- 
 mation where one costly transmitting station supplies a 
 great number of simple, inexpensive receiving stations, 
 seems a practical commercial problem, especially in localities 
 ill-equipped with land lines. 
 
 12. Proposals re future Work of Committee. As regards the 
 future work of the Sub-Committee, we can, if desired, examine 
 more fully the position of Radio Telephony abroad. We desire 
 to state, however, that from the general study which we have 
 made of the information published in the technical press, we 
 hardly expect to find that the development of Radio Telephony 
 in foreign countries has been carried much, if any, further than 
 in this country. We can, if desired, recommend to the Radio 
 Research Board a programme of investigation which could be 
 undertaken with a view to the improvement and development 
 of this means of communication. 
 
 H. B. JACKSON, 
 CECIL L. FORTESCUE, 
 G. W. 0. HOWE, 
 A. G. LEE. 
 
 O. F. BROWN 
 
 (Secretary). 
 
 Printed under the authority of His MAJESTY'S STATIONERY OFFICE 
 
 By Eyre and Spottiswoode, Ltd., East Harding Street, E.G. 4, 
 
 Printers to the King's most Excellent Majesty. 
 
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