WWII Prison Camp Short-wave Receiver
 
 

These drawings come from  United States Army in WWII, The Technical Services, The Signal Corps: The Outcome, U.S. Government Printing Office, 1966.  The text follows:

     “Nor was concealed radio activity by Signal Corps men in the Philippines confined to the guerrillas.  There was at least one incident of it in prison, involving a radioman, William D. Gibson, who had received his commission as a lieutenant in the Signal Corps only a few hours before the fall of Corregidor. A former U.S. “ham” working in Manila as a civilian radio technician, he had offered his services to the Army on Corregidor after the enemy invasion began.  But his commission had been delayed till the last hours of his freedom because the medical officers, busily treating wounded men, had not given him the required physical examination.  Subsequently, a prisoner in the Cabanatuan concentration camp, he came into the possession of a 1-tube regenerative radio receiver improvised by an officer of the Engineer Corps, Capt. Russell J. Hutchinson, who had built it of scrap parts and placed it inside a GI canteen.  Hutchinson, on being shifted out of the prison, left it with Gibson.  But the set no longer worked.  Its single amplifying tube, a 12SK7, had burned out. Obtaining a different type of amplifier tube, a 6J7, stolen by an American sailor who had a prison job in a Japanese shop, Gibson, rewired the set to accommodate the tube; a cauterizing iron from the prison hospital served as a soldering iron.  Looking like any ordinary canteen, the radio was kept hanging at the lieutenant's bed.  Japanese inspectors passed it by, suspecting nothing.  Its antenna was a No. 22 wire woven inconspicuously into a rope clothesline.  Only the headphones had to be secreted separately. The prisoners furtively operated the receiver in the evening, using battery power, which was available in the prison hospital.  The little set brought in radio programs emanating from Siagon, Tokyo, and San Francisco.  Best of all was the Voice of Freedom broadcast from the Apache after the Leyte Campaign began.  This treasured radio receiver was left behind when the lieutenant, suddenly freed with other prisoners departed in the pell-mell of the daring Cabanatuan raid, 30 January 1945.
 
 

Here's my reproduction of the radio.  I was suprised that the 12SK7 fit across the narrow dimension of the canteen.  I used a straight-forward regen circuit with a tapped coil and antenna coupling via a trimmer cap.  It tunes about 5 to 12 MHz.  A circuit of this sort will work with as little as 12 volts on the plate.  The standard canteen cup covers the opening when it's in the cover.  When you pick it up it just feels like a canteen.