TRANSMITTERS & TRANSCEIVERS

Harbour Transmitter for Rear Admiral of Destroyers

DATE OF DESIGN

1935

FREQUENCY RANGE

400 - 1000 kc/s

POWER SUPPLIES

HT 100V - ship's mains in series with 50V accumulator battery. LT - 2 x accumulator batteries.

RANGE IN MILES.

TYPE OF SET (VALVES USED)

VALVE

WAVEFORM

CW and ICW. For ICW, set modulates the HT at 1000 c/s.

ASSOCIATED WAVEMETER.

1492B or G7, G8, G9.

METHOD OF PRODUCING OSCILLATIONS

Master Oscillator.

WHERE USED/FITTED

Flagships Destroyers. To avoid delay in starting transmissions the power supply is independent of a motor generator which would take time to start. A coupled aerial is provided to reduce harmonics and interference to other lines of reception. Briefly, the set consists of a Master Oscillator driving a main or amplifier circuit to which the aerial circuit is coupled inductively. For ICW, a modulator circuit is used to modulate the HT supply to the amplifier valves at a frequency of approximately 1000 cycles. A diagrammatic picture of the complete circuit, including the battery charge-discharge arrangements is shown below. The set components are built into a completely screened aluminium framework which is housed in a wooden box.

This one-off set {which later, may have set a precedent for more stable and accurate transmitters - overtones of the Transmitter 4T and the Type 60 it served} was not given an 'outfit' or 'Type' letter/number. It was simply called "the harbour transmitter for Flagship Rear Admiral [Destroyers]. It is almost certain that each of the several Fleets had such a set, and each Fleet would have used a different frequency. Although the little handbook we have concentrated on the set's parameters and capabilities, there is a graph at the end of the book which tells us that it belonged to the Mediterranean Fleet.

The transmitter, was designed in 1935, and was specifically intended for controlling traffic on the destroyer wave in harbour and was, therefore, designed to maintain a stable frequency. Even in the early 1950's, the controlling of the enormous numbers of ships maintaining watch on a LCN (Local Command Net), Portsmouth callsign MTN (2649kc/s) or Plymouth [Devonport] callsign MTI (2705kc/s), was a major task for the operator in the Flagship or local shore station, and those ships (using 60's, 89's, 601 series in the main - but notwithstanding, all using crystal controlled sets), were at least 'on frequency' !

Here, the Flagship "netted" the circuit, and all ships tuned their transmitter to the zero beat resulting from the Flagships transmission, this irrespective of wavemeters etc.

FURTHER READING

PHOTOS, SCHEMATICS, DOCUMENTS

RA Harbour Transmitter Photos and Schematics.

NOTES.