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Motorola
  
BC-611   SCR-536
Special Forces hand-held two-way SW radio

BC-611, also known as SCR-536, 1 handy talkie or walkie talkie, was a valve-based hand-held two-way radio transceiver, developed in 1940 by Don Mitchell at Galvin Manufacturing (now: Motorola) for the US Army. It was used througout World War II (WWII), in particular during the landings on Sicily (Italy), North Africa and, in June 1944, at Omaha Beach in Normandy (France).

The radio is housed in a green water resistant enclosure that measures 320 x 90 x 80 mm and weights 2.3 kg, batteries included. It operates in simplex on a single channel (choosen from 50 channels) in the 80 m SW radio band between 3.5 and 6 MHz, using Amplitude Modulation.

The unit is powered by internal LT and HT batteries that are installed behind a hinged panel at the bottom. There is no power switch; the device is switched on simply by pulling out the antenna. At the side is a large PTT-switch and a shield on which the current frequency is written.
  
BC-611-F manufactured in 1945 by Motorola

The BC-611 was developed in 1940 by an team led by Don Mitchell, chief enigineer at Galvin Manufacturing (now: Motorola). It was the first true self-contained hand-held unit to be widely deployed and was mass produced from July 1941 onwards. By the end of WWII, 130,000 units had been made by Motorola. The BC-611 was also produced by other manufacturers, including ERLA.

After the war, the BC-611 remained in production in several countries until 1956, and was made under licence by various foreign manufacturers, including LGT in France, Autophon in Switzerland (sold as FOX SE-100) and NEC in Japan. In some European countries, such as The Netherlands, the BC-611 was used for several years after the war by the re-established Police Force [6]. The devices were also heavily used during the Korean War (1950-1953). For re-enactment, low-cost BC-611 reproductions (replicas) are available today from various sources [4].

A great historical account was given in 1977 by Elmer Wavering – former handler of governmental contracts at Galvin Manufacturing – who personally knew Don Michell — developer of ther BC-611 — and Paul Galvin — the company director — both of which had meanwhile passed away [7].

  1. SCR-536 is the designator of the complete radio set, whilst BC-611 refers to the transceiver only.

BC-611-F manufactured by Motorola
Model and serial number tag
Antenna with built-in power switch
BC-611-F with CS-81 Test Case
BC-611-F made in March 1952 by NEC
Model and serial number tag
Antenna with cover
Antenna without cover (partially extracted)
A
×
A
1 / 8
BC-611-F manufactured by Motorola
A
2 / 8
Model and serial number tag
A
3 / 8
Antenna with built-in power switch
A
4 / 8
BC-611-F with CS-81 Test Case
A
5 / 8
BC-611-F made in March 1952 by NEC
A
6 / 8
Model and serial number tag
A
7 / 8
Antenna with cover
A
8 / 8
Antenna without cover (partially extracted)

Models
During WWII, six models of the BC-611 were released, suffixed by the letters A-F. As the chassis doesn't carry a serial number, and the case is identical for all models, the interior doesn't always match the case and, hence, the model number. The repair manual provides help on identifying the different models [B]. Below is a non-exhaustive list of the most obvious differences:

  1. Initial version of the BC-611.
  2. Resistor R25 added.
  3. R28 added. Antenna support insulator added. 1,2
  4. Polystyrene antenna insulator instead of ceramic, Aluminium mic and speaker caps.
  5. Different PTT actuating linkage. Phenolic membranes.
  6. Sockets added for external microphone and headset (bottom cover assembly).
  1. Not on early BC-611-C models. This insulator had to be added to existing models when they were returned for repair, in accordance with MWO SIG 11-235-2.
  2. On BC-611-C units with manufacturer code CZE (made by ERLA), segments E and F of the Push-To-Talk switch (PTT) are swapped to allow for shorter connections.

Specials
Test Case   CS-81
When altering the channel (fitting different crystals and coils) or re-aligning the radio after a repair, it is necessary to remove the interior from its enclosure, and temporarily install it in the test case shown in the image on the right.

The Test Case is nearly identical to the original enclosure, but has holes in its body through with the adjustment points can be reached. Once alignment is complete, the interior can be re-installed in its own enclosure.
  
CS-81 Test Case for BC-611-F

NEC version   Japan
A rather unique example of a post-war BC-611-F, is the one shown in the image on the right. It was manufactured in March 1952 by the Nippon Electric Company (NEC) in Tokyo (Japan).

The unit shown here is configured for 5127.5 kHz and has serial number 00001.
  
BC-611-F made in March 1952 by NEC

BC-611-F with CS-81 Test Case
CS-81 Test Case for BC-611-F
BC-611-F made in March 1952 by NEC
Rear side
Battery compartment
Model and serial number tag
Antenna with cover
Antenna without cover (partially extracted)
B
×
B
1 / 8
BC-611-F with CS-81 Test Case
B
2 / 8
CS-81 Test Case for BC-611-F
B
3 / 8
BC-611-F made in March 1952 by NEC
B
4 / 8
Rear side
B
5 / 8
Battery compartment
B
6 / 8
Model and serial number tag
B
7 / 8
Antenna with cover
B
8 / 8
Antenna without cover (partially extracted)

Specifications
  • Device
    Handheld two-way radio
  • Developer
    Don Mitchell
  • Manufacturer
    Galvin Manufacturing (Motorola), span class)
  • User
    US Army
  • Year
    1940
  • Production
    1941-1956
  • Quantity
    130,000 (by the end of WWII)
  • Frequency
    3.5 - 6 MHz
  • Band
    80 m (SW)
  • Channels
    1 (from a set of 50) 1
  • Spacing
    40 kHz
  • Modulation
    AM
  • Sensitivity
    3 - 5µV
  • Valves
    5 (see below)
  • Output
    360 mW
  • IF
    455 kHz
  • Antenna
    1 m (40") telescopic rod
  • Range
    200 m - 1.6 km (over land), or 4.8 km (over salt water)
  • Batteries
    LT: 2 × BA-37 (1.5V)
    HT: 1 × BA-38 (103.5V)
  • Current
    LT: 250 mA (300 mA when transmitting)
    HT: 11 mA (35 mA when transmitting)
  • Duration
    ~ 1 day (19 hours)
  • Weight
    1.75 kg (2.3 kg with batteries)
  1. Channel selected with plug-in crystals and coils. Each unit is aligned for a single channel.

Valves   Tubes
  • 1 x 1R5
    VT-171
  • 1 x 1S5
    VT-172
  • 1 x 1T4
    VT-173
  • 2 x 3S4
    VT-174
Accessories
  • BX-48
    Box for spare crystals and valves (5 sets)
  • BX-49
    Box for spare crystals and valves (24 sets)
  • BG-162
    Bag for batteries (BA-37, BA-38)
  • CH-146
    Chest for equipment
  • CH-233
    Chest for spare tubes, crystals (400 items)
  • CH-312
    Test case for IE-37 tuning unit
  • CS-144
    Parachute case
  • CS-156
    Canvas case
BC-611-F only
  • HS-30
    Headset
  • T-30
    Throat microphone
  • T-45
    Upper lip microphone
Options
  • ME-36
    Maintenance kit
  • MC-619
    Homing modification
  • MC-534
    Frequency conversion kit
  • MC-518
    Frequency conversion kit
  • IE-15-A
    Test Equipment
  • FT-252
    Test Stand
  • CS-81
    Test Case
  • I-56
    Test Set
  • IE-17
    Test Equipment
  • I-135
    Test Unit
US manufacturers
Foreign manufacturers   post-war
Nomenclature
  • BC-611
  • SCR-536
  • Handy Talkie
  • Walkie Talkie
  • Banana
Related patent
Documentation
  1. TM 11-235, Radio Sets SCR-536-A, -B, -C, -D and -F
    US, War Department, May 1945.

  2. TM 11-4019, Repair Instructions
    US, War Department, July 1945.
References
  1. Wikipedia, SCR-536
    Retrieved June 2022.

  2. Gil McElroy (VE3PKD), A Short History of the Handheld Transceiver
    ARRL. QST, January 2005.

  3. Klaus-Peter Jung (DH4PY), Bananas
    Retrieved June 2022.

  4. 90th Infantry Division, What Price Glory, BC-611 Radio Reproduction
    25 May 2014.

  5. Radiomuseum, SCR-536 Radio Set BC-611 (Variants A, B, C, D, E and F)
    Retrieved June 2022.

  6. Scannermuseum, Etherbeheer: Verbindingen bij de Amsterdamse Politie
    Visited 7 June 2022.

  7. Elmer H. Wavering, Letter to Mr. T.F. Walkowicz
    Galvin/Motorola, 23 March 1977.
Further information
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Crypto Museum. Created: Tuesday 07 June 2022. Last changed: Thursday, 11 August 2022 - 09:11 CET.
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