In reply refer to Initials  
             and No.  
     
 
NAVY DEPARTMENT
 
 
OFFICE OF THE CHIEF OF NAVAL OPERATIONS
 
 
WASHINGTON
  
  Ser.  #Z-0250  
                                                                                      June 1, 1943.  
     
     
  MEMORANDUM for Colonel Catesby ap C. Jones, G.S.C.,  
                                      Chief, Prisoner of War Branch, G-2.  
     
 
SUBJECT: Spot Item.
   
Enclosure: (A)  Sport Item No. 76.
 
     
          1.        Enclosure (A) constitutes information contained in statements made by three radio rating survivors from a german submarine.  Because of its nature, the material is being given limited dissemination in this form and will not be included in the interrogation report given general distribution.  
     
          2.        Attention is invited to the fact that this material is drawn from prisoner of war sources, and that, while believed to be reliable, it may be subject to later correction or modification from other sources.  
     
     
                                                                                
                                                                                             John Riheldaffer,  
                                                                                  Commander, U.S. Navy, (Ret.),                 
                                                                                 Head of Special Activities Branch,  
                                                                                    Division of Naval Intelligence.  
     
     
 
 
 
 
     

 

 

 

 
 
 
 
  No. 76  
     
  SECRET  
     
 
PRELIMINARY REPORT ON THREE RADIO RATINGS FROM U-203
 
     
 
Call-signs         U-203's call sign was UIL which agrees with previous information.  It was impossible to get any definite information about the use by boats of call signs.  One man admitted that they might be used in relay procedure.  It was understood, however, that there are no call-signs concealed in the text, as distinct from Address Groups which in the nature of things often have to be included.  U-boats may always transmit if the channel is clear without calling any other boat or station.  Control will always automatically take down every signal on its frequency
   
Enigma         Whether in Enigma or any other type of signal the clear text is handed to the operator for encyphering.  All the radio ratings were agreed that no type of signal is ever re-cyphered.  The clear text is typed on the machine and is then ready for sending.
   
          The impression was given that the Kenngruppen (the first two groups which are always repeated at the end) are not used to set the machine, the setting being changed automatically at the correct time and the TOO being therefore of great importance.  It appears probable that these groups are coded and contain a priority if required.  The most important evidence of priority, however, lies in the type of signal, - Alpha, Beta, and Enigma messages being given priority in that order.  No priority is visible until some part of the signal has been de-coded.
   
          The signature was definitely stated not to be in the Kenngruppen.  Prisoners suggested that the signature sometimes took the form of the boat's number at other consisted of the Commanding Officer's name.  They stated that
 
     
 
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  No. 76  
     
  SECRET  
     
 
  it is not an invariable rule always to include the boats position in every signal.
   
          All the prisoners state that it is not possible to say what the average length of a signal reporting a convoy would be since the amount of information as to the composition of the escort and convoy varies greatly.  Generally speaking an average of 20-30 groups might be approximately correct.  After a successful attack the result must be reported, but it is left to the Commanding Officer's discretion when to do so.
   
          The C.O.'s permission is required in order to start transmitting.  Apart from this fact a signal will always be sent as soon after it has been originated as the operator can manage.  Prisoners said that the C.O. himself inserts the TOO, and states what type of signal he wishes to have sent.
   
WW(Willi) Signals
   
  All prisoners gave no evidence of disagreement with the assumption made towards these signals by interrogators that they are purely weather signals.  By various indications, however, they confirmed the correctness of the assumption.  The impression was given that they are always weather signals.  THese signals always consist of 4 groups; formerly they consisted of three.  Prisoners stated that the change was made to allow a new category of information to be inserted.  THe data includes wind direction and strength, and atmospheric pressure.  It was not possible to discover what each of the categories is but it was said that they never vary and that each WW signal contains the same information.  They do not contain a position.
 
 
 
 
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  No. 76  
     
  SECRET  
     
 
          The signals are only sent on request, generally at night.  The number of reports requested in a day varies considerably.  Operators only have a chance to estimate the number on their own frequency and state that often none at all is ordered on one particular frequency on a single day.  It is not only boats returning home which are ordered to make such signals.
   
          Prisoners ridiculed the idea the WW signals ever consist of seven groups and end with a two-letter group.  Only Beta signals ever end with a two-letter group and WW signals always consist of four groups.
   
Alpha Signals         The 3-figure group at the beginning is in no way particular to one U-boat.  The impression was given that these signals are used only for the sake of priority and speed of sending.
   
Frequencies         Before sailing a U-boat is fully informed of the schedules in force consisting of the Schaltung (group of frequencies) and the frequencies used within it at various times.  A boat always remains on the same Schaltung until ordered to change to another.  She will use the appropriate frequency for the time of day within that Schaltung.  At any one time all the boats operating on the same Schaltung, which corresponds roughly to a large geographic area, will be on the same frequency both for reception and transmitting.  There is never a choice of the frequency for reception, but if, for any reason, difficulty is experienced in clearing an outgoing signal from a boat to the shore, the operator may with permission of the C.O. switch to another Schaltung and use the frequency which is appropriate to this new
 
 
 
 
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  No. 76  
     
  SECRET  
     
     
     
 
  Schaltung at that time.
   
          The frequency schedule is sometimes changed when a boat is at sea and notification is received by signal.  This in fact happened during U-203's last patrol (April 3 to April 25), but in the normal course of events an unless a particular reason occurs for altering the schedules they continue in force or are changed according to a fixed scheme which is known before departure on patrol.
   
          Evidence from U-203 and many other U-boats goes strongly to show that while ultra high frequency is carried by U-boats when on trials and working up in the Baltic, it is invariably removed before going out on patrol.
   
          The frequency indicators given by Ottawa appear to be correct.  Prisoners volunteered the information that on her last patrol U-203 used inter alis PF and SA which are both listed as being amongst those used in Series A.
   
Control         When a signal is made by control to a U-boat at sea requiring an answer, control will transmit that signal for the correct number of times under the "schema" in use, whether the U-boat has replied in the meanwhile or not.  When possible the answer will be sent immediately on receipt of the signal requesting it.
   
          While it used to be true that some signals carried three serial numbers (Leitnummer) this is never done any longer.  Prisoners would not say what significance signals with several numbers used to have, but all stated that it would not require much intelligence to figure it out for oneself.
   
          JIA' is the control for the "Aüstankurzwelle" (Coastal short wave) and is possibly near Paris.  It uses serial numbers from 001 - 100.
 
 
 
 
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  No. 76  
     
  SECRET  
     
     
     
 
Miscellaneous         U-boats do not listen to allied frequencies or to 500 kcs.  They sometimes, however, hit upon the secret station Gustav Siegfried Eins by mistake.
   
           It was stated that one boat never sends signals for several others in a group.
   
          A good operator should be able to change from one frequency to another when transmitting in about 5 minutes.
   
          Two Enigma machines are carried on board, only one being used at a time.
   
          The maximum power input to the final stage (Endanodenstrom) in a 500 or 750 ton U-boat's transmitter is 1500 watts.
   
          No trouble is said to be encountered with the DC high voltage supply and a hum does not develop in the transmitter.
   
          It is not the practice in U-boats to listed to the "Kameradschaftsdienst".
   
          It is at the discretion of the operator whether or not he starts a Beta signal with Vu.
   
Radio Operators
   
          All medium sized U-boats, as far as is known, carry a complement of four operators, generally two senior and two junior.  The seniors must have taken petty-officers' courses and are, to the extent, greater experts in handling the equipment.  All four, however, can and usually do transmit.  They are always in two watches, one senior and one junior being on watch at the same time.
 
 
 
 
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  No. 76  
     
  SECRET  
     
     
     
 
          Operators are often recognizable by their "fists" and apparently no great effort is made in school or otherwise to discourage the development of a fist, U-boats invariably use an ordinary key and not a "bug".  Prisoners do not themselves know how they slow down the sending of a Beta signal, but are inclined to think that the reduction in speed is a combination of lengthening the dashes and the intervals.
   
          The senior operators on board have sufficient knowledge to make repairs to a transmitter at sea and, in fact, often have to do so when a boat is damaged.  All radio equipment is overhauled by base personnel every time a boat returns from patrol.
   
   
   
   
   
   
   
   
   
   
   
   
   
 
 
 
 
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