U-boats maintained separate logs of radio messages and a summary of these were submitted as an attachment to the KTB.  The CO often noted messages pertinent to the tactical situation in the KTB usually noting the sender and enclosing the text in quotes.   
         For a general description of U-boat communications see the excerpt on Communications from the Cumulative Edition.  

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Excerpt on German U-boat Communications from the Cumulative Edition - CB 04051(103) The Admiralty's appreciation of the German U-boat force as of June 1944
          The links below provide information on U-boat communications equipment and procedures.  Dirk Rijmenants' and Tony Sale's pages on cipher machines cover cryptography, the Enigma machine, the role of cryptology in the U-boat War and many other topics.  The Foundation for German communication and related technologies presents excellent pages on U-boat communications, Kurier, the T 200FK 39 transmitter and many other communications and radar technologies.  Helge Fykse's and Yuri & Vladimir Desyatnik's pages present thier excellent collections of German WWII radios as well as links to other collectors.  
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  Dirk Rijmenants' pages on Cipher Machines and Cryptology
  Tony Sale's Codes and Ciphers in the Second World War
Foundation for German communication and related technologies (see the T200FKW39, Köln E52, T9K39 Main, Spez 406/S, Lo1UK35 and many articles on communications)
  Bruce Culp's pages showing close-up, high-definition photographs of U-boat radio equipment
  Helge Fykse's WWII Radio PagesTelefunken (see the Köln E52, Lo40K39 and Lo 1 UK 35)
          German names for frequency bands were not the same as the Allied system also radio bands were sometimes referred to by wavelength in meters instead of frequency.  These terms are set forth in the table below.  
German System
Allied System (still in use today)
German Name
Frequency Band
Allied Equivalent
Frequency Band
Längstwelle (LäW - very-long-wave) below 100kHz Very low frequency (VLF) 3-30kHz 10-100 km
Langwelle (long-wave) 100kHz-1.5Mhz Low frequency (LF) 30-300kHz 1-10 km
Grenzwelle (intermediate-wave) 1.5-3MHz Medium frequency (MF) 300kHz-3MHz 100-1000 m
Kurzwelle (KW - short-wave) 3-30 MHz High frequency (HF) 3MHz-30MHz 10-100 m
Ultrakurzwelle (very-short-wave) above 30MHz Very High frequency (VHF) above 30MHz 1-10 m
Ultrakurzwellen are subdivided into:
Meterwelle Meter wave
Dezimeterwelle Decimeter wave
Zentimeterwelle Centimeter wave
Note:  adapted from the Cumulative Edition - CB 04051(103)
          When discussing WWII radios and communications it is often necessary to convert from wavelength to frequency.  The link below is an easy to use converter.   
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  Frequency and Wavelength Calculator
  German WWII Phonetic Alphabet  
A Anton I Ida R Richard
Ä Ärger J Jota S Sophie
B Bruno K Karl T Toni
C Cäsar L Lucie U Ulrich
Ch China M Max Ü Übel
D Dora N Nanni V Victor
E Emil O Otto W Wilhelm
F Fritz Ö Öse X Xanthippe
G Gustav P Paula Y Ysop
H Hans Q Quatsch Z Zet or Zeppelin
Additionally a number of Greek letters were used for special purposes
α Alpha δ Delta λ Lambda
β Beta ε Epsilon π Pi
γ Gamma        
  U-boat Radio Equipment  
          U-boats carried a suite of radio equipment giving them the ability to transmit, receive and direction find on several frequency bands.   At the beginning of the war all HF and MF transmitters used forward jumping wire/antenna and the U-boat received HF transmissions on the trailing jumping wires/antennas.  Because of the polarization of the wire, the boat sometimes had to point perpenticular to the station it was transmitting to or receiving from.   Later a telescopic rod antenna extending from the port side of the bridge was added but this did not prove successful and was later removed in favor of the radar antenna.  U-boats received and transmitted messages in encrypted Morse code.  U-boats seldom, if ever, transmitted or received by voice.  The boat would have to be surfaced to transmit or receive messages on HF but could receive messages on VLF when submerged at shallow depth using the DF-loop antenna.  U-boats communicated almost exclusively with Control ashore.  They did not send messages or beacon signals to other U-boats unless instructed to do so by Control.  A typical radio suite would consist of the following equipment:  
Frequency Band
Primary transmitter (Type IXD carried 2)
Ship to shore message traffic in encrypted morse code
Back-up transmitter
Ship to shore message traffic in encrypted morse code
Beacon transmitter
Sending beacon signals to other U-boats and aircraft
Ship to Ship Voice
Early war carried during working-ups, later used for communications intercept
Emergency beacon
Liferaft beacon transmitter
Primary receiver
Ship to shore message traffic in encrypted morse code
Back up "all wave" receiver
Also served as VLF receiver using DF Loop antenna
Beacon receiver
Receive and DF beacon signals from other U-boats and aircraft, VLF message traffic submerged using DF Loop antenna
Broadcast receiver
News/Entertainment. Used the DF Loop antenna.  Had jack for record player and could be connected to ship's announcement system
        The following is a list of radio equipment used aboard U-boats.  It is compiled from several sources and it is hoped to expand it.
Primary use
Telefunken Spez 406S/36 3.75-15 MHz (HF) 200W
Primary HF Tx.
Telefunken T200FK39 3-23 MHz (HF) 200W
Lorenz Lo40K39 5-16.7 MHz (HF)
Backup HF Tx.
Telefunken Spez 2113 300-600 kHz 150W
Beacon MF Tx.
Lorenz Lo10UK39 37.8-48 MHz (VHF) 10W
Ship to Ship Voice
Transceiver - Early war only on workups - later used for communications intercept
Lorenz Lo1UK35 41.55-45.75 MHz (VHF) 10W
Fieseke & Höpfner NS2 or Phillips NS2a 600m/500 kHz 8W
Emergency beacon
For use in lifeboat, hand crank power supply, automatically sent SOS signal had box kite aerial
Telefunken E437S 1.5-25 MHz (HF)
Primary HF Rec.
"Bread Box"
Telefunken T9K39 1.5-25 MHz (HF)
Telefunken E52 1.5-25 MHz (HF)  
Telefunken E436S 74 kHz-1.5 MHz (VLF-HF)  
Early war Rec.
Telefunken E381S 15 kHz-20 MHz (VLF-HF)
Backup HF Beacon and VLF Rev.
"All wave Rec."
Telefunken T3PLLä38 15-33 kHz /70-1200 kHz (VLF/LF)  
Beacon and VLF Rec.
Used DF Loop antenna
Telefunken E 405 N 15-33 kHz/65-1667 kHz  
Early war Rec.  Navy modified EP2
Telefunken ELA 1012a/b 145 kHz-21.8 MHz (LF/HF)
Broadcast Rec.
News/entertainment used DF Loop antenna, Had jack for record player, could be connected to the boat's announcement system
Radione R2 150 - 428 kHz (LF/MF), 508 - 1560 kHz (MF), 5.9-22.2 MHz (HF)
Broadcast Rec.
News/entertainment used DF Loop antenna, portable - often mounted in officers or captain's cabin
Other Equipment
KZG 44/2 Kurier pulse generator  
Einheitsbetriebsgerät (EGB) Remote transmitter control panel for use with HF transmitters  
KWS Frequency control apparatus
2 x Antennenwahlschalttafel Antenna selector panels - used to switch transmitters or receivers to various antennas
Schlüssel-M (Enigma machine) Used to encode messages for transmission  
Note:  adapted from U-boats, The Illustrated History of the Raiders of the Deep, by David Miller, with information from History of Telegraphy by K. G. Beauchamp, Type VII U-boats, by Robert C. Stern and Ubootwaffe, Marine - Kleinkampfverbände 1939-1945 by Waldemar Trojca.
Radar Detectors - Funkmess-Beobachtung (FuMB)
FuMB 1 Metox 600A 130-260 cm FuMB Ant. 2 Honduras (Biscay Cross) Manual Loudspeaker-Headphone Intro. Aug 42
      Rotated by hand rough DF   Magic eye (later models) Banned Aug 43
FuMB 8 Wanze G1 - Zypern I 120-180 cm FuMB Ant.  3 Bali - Runddipol Automatic 24 x/sec. Cathode ray tube Intro. Aug 43
      Fixed no DF Manual fine tuning Loudspeaker-Headphone Banned Nov 43
FuMB 9 Wanze G2 - Zypern II Same as Wanze G1 except that receiver did not radiate and had variable speed automatic search
FuMB 10 Borkum 20-300 cm FuMB Ant. 3 Bali - Runddipol Untuned Loudspeaker-Headphone Intro. Nov 43
      Fixed no DF      
FuMB 7 Naxos 8-12 cm FuMB Ant. 11 Finger Automatic Loudspeaker-Headphone Intro. Sept.-Nov. 43
    8-12 cm FuMB Ant. 24 Cuba Ia - Fliege     Intro. Feb 44
    2-4 cm FuMB Ant 25 Mucke     Intro May 44
      Rotated rough DF      
FuMB 26 Tunis 2-4 cm and 8-23 cm FuMB Ant. 24 Cuba Ia - Fleige (for 8-23 cm wavelengths) and FuMB 25 - Mücke (for 2-4 cm wavelengths) antennas back to back.  Automatic Cathode ray tube and Headphones - Loudspeakers Intro. June 44
      Hand rotated rough DF      
FuMB 35 Athos 2.5-4 cm and 8-15 cm Not numbered Automatic Cathode ray tube and Headphones - Loudspeakers Intro early 45
      Fixed with electronic DF    
FuMZ 10 Puck 901 10 cm Test signal generator for FuMB gear      
U-boat Area Circuits  
Gebiet Schaltung U-boat Area Circuits - Used to provide communications in a specific area.  Frequencies were chosen to optimize reception for day and night in each area.  Messages numbered sequentially for each U-boat so that the radio operator would know if a message was missed.  They were transmitted on HF at set times and repeated on VLF.
Küste (Coastal) Channel and Biscay area
Ierland (Ireland) Eastern North Atlantic
Amerika (America) und Afrika (Africa) Schaltung America and Africa circuits consisted of three separate circuits each in which two channels or frequencies were generally keyed simultaneously
    Amerika 1, A&B Eastern North Atlantic
    Amerika 2, C&D Western Atlantic north of line from Azores to Key West
    Amerika 3, E&F Middle Atlantic, Caribbean and South American coastal areas
    Afrika 1, A&B East Atlantic and Indian Ocean
    Afrika 2, C&D         "                                "
    Afrika 3, E&F         "                                "
Arktis (Artic) Controlled from Norway - Northern Norway and Murmansk convoy routes
Mittelmeer (Mediterranean) Controlled from Toulon - Western Mediterranean
Ägäis (Aegean) Controlled from Salamis - Eastern Mediterranean
Penang Controlled from Penang - Indian Ocean area supplementing the Africa services
U-boat Convoy Circuits  
Konvoi Schaltung Convoy circuits - Used to separate communications for U-boat groups from U-boats not part of the group.  Either Diana or Hubertus was always in effect sometimes both simultaneously
Diana Convoy circuit
Hubertus Convoy circuit
Wotan Only active a short time late in the war
Other Circuits  
Bruno 3 (Norddeich) Four frequencies keyed simultaneously.  Frequencies were chosen to provide world-wide coverage.
Anton (Kootwijk) Four frequencies keyed simultaneously - Used in the Eastern North Atlantic and Northern Norway



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