WWII SIGNAL CORPS BALLOON AERIAL, 1943

Second World War Aerial Balloon in tin container. Once opened by a Sardine key, the balloon was filled with Hydrogen and the aerial wire attached.

Your comments:

• All correct. The shapely Gibson Girl Transmitter designated BC778 with versions though to BC778-F.
  
  Coloured bright yellow to be more readily seen in the water was held between your legs for ease of use and was quite complete kit for airmen lost at sea. they weighed about 30 lbs.Power input was about 5 watts.
  
  Frequencies (transmit only) were 500 kHz ( SCR-578/BC-778 ) 500 kHz and 8280 /later 8364 kHz ( AN-CRT3) The set could be switched to 'auto' where cranking the handle transmitted "SOS" continually from memory interspersed with a 1000 cycle tone...on 8364 kHz or 500 kHz (kC's) and could be manually keyed on 8364 KC's...chosen as an international emergency communications channel.
  
  I actually do not recall them having the higher frequencies on the ones I saw long ago so that may have been 'later'.
  
  I also do not recall seeing a crystal in them so the information I have chased up may be half correct....just a crystal on the higher frequency when that came about. I am pretty sure the earlier ones were just an inductor/capacitor achieved frequency.
  
  
  You could send SOS as an alert and then switch to the international frequency hopefully to be heard as to situation. location etc. It was a process of repeat and repeat....and repeat until, hopefully, rescued.
  
  It used a 12A6 and a 12SC7 tube in the circuit
  
  The kit also had a (head mounted) lamp which would flash the Morse at night through the lamp or just repeated flashing for visibility...if you chose that way. The handle was to be cranked at about 80 rpm.The range was up to about 300 miles on 500kHz(kC's) to an air plane at 2000 feet and about 1500 miles on the higher frequencies...if the 300 ft long antenna (hidden inside that round lid with the black control) was hovering well.
  
  That antenna length was needed not simply for height in this perfect transmitting location with the sea as 'ground" but to handle the low 500kC's frequency. Tuning was done using simple panel mounted tuning-lamp brighness...less likely to be damaged than a meter and also can be seen at night.
  
  Modes...Auto 1: sends automatically: SOS (20 Sec) , then a tone (20 Sec), repeats.
  Auto 2: sends automatically: AA (20 Sec) , then a tone (20 Sec), repeats
  Manual: Morse key (source green radio)
  
  The unit was comprised of a balloon antenna but also a kite antenna...quite a brilliant survival arrangement for your raft. The could be dropped by parachute. The set was actually designed from a captured German survival radio transmitter "German "Notsender NS2". In 1941 one of these Notsender was captured by US forces. They added a few improvements and from 1942 on the SCR-578/BC-788 was produced.
  (source green radio)
  
  •Gibson Girl
  •T74 CRT-3
  •Crank Operated
  •8364 KC automatic
  •500 KC manual
  Complete with the following parts:
  
  •Quantity 1: Transmitter AN CRT-3
  •Quantity 1: Kite M-357-A
  •Quantity 2: Balloon Valve M-278-A
  •Quantity 2: Antenna Assembly AS-207
  •Quantity 1: Signal Lamp M-308-B p/n 85-0074-1
  •Quantity 2: Hydrogen M-315-B
  •Quantity 1: Bag BG-155-A nsn 5820-00-217-7166
  
  These were for sale in the 1960's new and complete for about Pounds Australian 20! in Australian disposals stores...complete kits were about twice that...
  
  They were used up to the mid 1980's in some places.
  
  
  
  
  
  .......... Tony Clancy, Sydney Australia, 18th of November 2013
  
  
• Part of the Gibson Girl dingy or lifeboat kit. The transmitter was hand cranked to generate the voltages for the transmitter inside. The kit included a kite and a balloon which could be filled with this gas canister, either of which carried the wire antenna aloft.
  .......... Ben Nock, Military Wireless Museum., Kidderminster, Worcestershire., 25th of February 2012
  
  
• These balloons were usually filled with hydrogen. It was often produced in a small vacuum-sealed tin-can generator, which used calcium hydride. (This produces hydrogen when exposed to water, exactly as acetylene is made in lamps using calcium carbide.)
  .......... Anthony Bullock, Gloucestershire, England, 23rd of April 2011
  
  

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