1619/223 DATED 9TH MAY, 1943.
               Convoy ONS5 was routed through an area between Newfoundland and Greenland in which H/F ship-shore communication proved extremely difficult and unreliable.
          2.  In spite of this, however, there were often considerable delays in the rebroadcasting of operational signals originated by ships at sea.  
          3.  On 2nd May there were delays of eleven and thirteen hours, respectively, between the times of despatch from DUNCAN of two IMMEDIATE signals and their subsequent reception on broadcast "L".  As a result the Third Escort Group were considerably delayed in their meeting of Convoy ONS5 since these signals contained important information concerning the movements of the latter.  
          (a)  A.I.G. 303 (R) A.C.I. (C), Escorts ONS5, E.G.3.    from B.7.  
                T.O.O.  012000Z.  
                T.O.D.  020312Z (by DINCAN).  
                T.O.R.  021415Z (by OFFA as message 482L on 105 kc/s).
          (b)  A.I.G. 303 (R) A.C.I. (C), E.G.3.        from B.7.  
                T.O.O.  010801Z.  
                T.O.D.  020136Z (by DUNCAN).  
                T.O.R.  021440Z (by OFFA as message 486L).  
          4.  Two IMMEDIATE messages from E.G.3, both of which were repeated to ships at sea were despatched to Iceland W/T at 0235Z and 0240Z on 4th May.  They were subsequently rebroadcast on 105 kc/s and received as messages 685L and 677L respectively at 1243 and 0925 on 4th May.  
          5.  When in contact with the enemy traffic on convoy R/T wave becomes heavy and continuous.  It can be reduced by:   
          (a)  Use of V/S whenever possible by day.  With Convoy ONS5 ships of close escort continued to pass Fleet Code and Nyko messages to each other on convoy R/T even when within easy V/S signalling distance.  
          (b)  Whenever possible use of HT11 frequencies given in W.A. General Message 631N for intercommunication between Senior Officers of Close Escorts and Support Groups.  
          6.  When in contact with the enemy the proportion of traffic on convoy R/T wave which is in Nyko or Fleet Code is as much as the Coding Staff of a small ship can deal with, irrespective of the decoding of messages received on the area broadcast.  (For a period of 24 hours on 4/5 May OFFA received 388 signals.).  
          7.  General Messages transmitted on area broadcasts must therefore be reduced to a minimum and all messages must bear appropriate delivery groups.  
          8.  It is considered that in Area D the coding problems of small ships could be considerably reduced:  
          (a)  by the introduction of the following Address Indicating Groups, together with their appropriate delivery groups, British-U.S. call signs and cypher groups.  
                  (i)  Ships and Authorities in Area D.  
                 (ii)  CINCWA's daily situation reports.  
                (iii)  NSHQ Ottawa's daily U-Boat estimate.  (The address of this signal now takes 25 groups of cypher.)  
  Signals (i) and (ii) above at present bear no delivery groups when transmitted on broadcast I.  The encoded address GB7A is one likely to be misunderstood by ships newly entering the area.  
          (b)  By reducing the number of general messages transmitted to GB7A on the area broadcast.  At present the substance of every W/T report from a ship at sea concerning enemy activity is broadcast as a fresh general signal.  Since the original signal will normally have been repeated to any ship's concerned and will therefore be rebroadcast much duplication of traffic is caused.  
                                                                                                      (9.   . . . . . . . .  


                                                                                                                                      Page 2.  
  Appendix II (Contd).  
          9.  The following four signals are examples.  
  A.I.G. 302, Escorts SC128, E.G.1.                                                                 E.G.3.
          ORIBI sighted U-Boat on surface in position 55 30 N  42 20 W (X).  U-Boat now dived.  Weather report 3280 3466.  
                                       (Rebroadcast as 751L.  T.O.R. 2142Z.)  
  GB7A (R) A.I.G. 303.                                                                                      CINCWA.  
          Submarine sighted by ship in position 055 30 N  042 20 W at 1950Z.
  A.I.G. 303.                                                                                                          TAY.  
          ONS 5 attacked in position 55 N  43 W.   3 ships sunk.  
                                         (Rebroadcast as 786L.)  
  GB7A.                                                                                                                 CINCWA.  
          3 ships attacked and sunk by submarine in position 55 N 43 W at 0130Z.  
          10.  Recent experience on the Northern route has shown the necessity for a more simple signal in Nersigs Vol. I (B.R.637) for "Ice in sight" or "Have encountered ice".  A signal which can be hoisted, flashed or sounded on the syren is required.  
          11.  H/F D/F.  
          Analysis of bearings obtained by ORIBI and TAY from 4th to 6th May indicate:  
          (a)  That attacking U-Boats were continuously using lines 1 and 2 of Series Two during this period.  
          (b)  That W/T transmissions on ahead bearings increased greatly for some two hours preceding the daylight attack at 1930Z on 5th May.  
          (c)  That during the period 1700/4 to 0200/5 when U-boats were concentrating and carrying out their attacks those on starboard beam and astern of the convoy used line 2 and those ahead and on the port side line 1.  After the first attack, however, the relation between frequencies used and relative bearing from convoy became confused and no further deduction could be drawn.  



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