RED ARMY RADIOTELEGRAPH SIMULATOR
Grimsby Beam Station/GBI
Type: PTT (P)
Transmitter station: Tetney
Receiver station: Skegness, Winthorpe
Operational office: London
Receiver end station: Dhond, 50 miles E of Poona
Transmitter end station: Kirkee/VWZ, 75 miles SE of Poona
Operational office: Poona
Callsign GBI was dedicated callsign for radiocommunication with India and South Africa.
2 waves were in use: 35 and 16 m (rounded to full kHz) :
35m - NIGHT
16m - DAY
Similiary like GBH 5 channels multiplex transmitter was in operation.
At that time that what we know as maritime radiotelephone band on 8.7 Mhz was very popular fixed service band.
Althought in my sources 19m was refered as 2 highest freqs I think it was exactly the same as 35m wave.
Since there is night and day band it is easy to guess how they operated:
1130-1730     DAY FREQ         telecom_opchat_dx() at zero freq.
2330-0530     NIGHT FREQ     telecom_opchat_dx() at zero freq.
00-50 min   High Speed Morse at 150 WPM
50-00 min   V tape is sent
 Commercial Short Wave Wireless Communications, part 1, Marconi Review 1929-10
 Commercial Short Wave Wireless Communications, part 2, Marconi Review 1929-11
 The History of Shortwave Radio in Australia
 Przedląd Radjotechniczny 9-10