TRANSMITTERS & TRANSCEIVERS

Type 81 Transmitter

DATE OF DESIGN

1921

FREQUENCY RANGE

750 - 1500 kc/s

POWER SUPPLIES

Ship's DC Main either 220V or 100V. The set has a nominal range of 2 miles is using 220V but this is considerably reduced with a 100V system.

POWER TO FINAL STAGE.

TYPE OF SET (VALVES USED)

WAVEFORM

RT and ICW

ASSOCIATED WAVEMETER.

1492B or G9

METHOD OF PRODUCING OSCILLATIONS

WHERE USED/FITTED

Type 81 is a low power valve set which was originally designed as an R/T transmitter but is now modified and has a separate attachment fitted for transmitting ICW. The set can be operated from either of three fixed positions, usually W/T office, bridge/chartroom areas and Auxiliary W/T office. The switch allowing this is marked "operator" and "control". When set to "operator" the local (main W/T Office) Morse key/microphone is operable and when set to "control" both remote positions and the W/T office operator can operate the set. Further, each position has a 'local' and 'remote' switch. When in 'remote' the operator at that position can key the transmitter and the other two operators can listen in to what is being said or tapped out on the Morse key. All three operators can converse (passing procedural information or engineering/operating instructions) without transmitting live, by each switching to their 'local' position and to 'R/T'. In this case the power is provided by a 4.5V dry battery.

FURTHER READING

IMAGES, PHOTOS, DOCUMENTS, SCHEMATICS ETC.

Full Schematic
Type 81 Photo

NOTES.