CONTINUING with the theme of maritime radio within the Port of Sunderland, many readers will recall the mysterious lattice steel wireless mast, which towered above Roker Block yard until the early 1990s.
Constructed in 1955, the structure was used as a marine radio beacon as part of a scheme to aid safe navigation around the coasts of the British Isles.
This involved groups of up to six different radio beacons transmitting on the same frequency.
Each radio beacon station within a group would transmit its unique call sign in Morse code for one minute, in turn, during a six-minute cycle. By international agreement, the Low Frequency band between 285 and 315 Kilohertz (KHz) was allocated for use by marine radio beacons.
Grouping of stations was planned to allow vessels obtain an accurate position fix by taking cross-bearings. As some stretches of coastline were too extensive for continuity of beacon coverage, marker stations were placed at various intervals to fill these gaps.
Sunderland was designed as a duplicate marker and calibration beacon, operating only during fog and for calibration of ships’ direction finding equipment.
The station’s call letters, KP, broadcast on 294.2 KHz, could be received within a 20-mile range when the beacon was being used as a marker station. It was also capable of transmitting signals at a reduced range of five miles for calibration purposes.
Supplied by Marconi’s Wireless Telegraph Co Ltd, the beacon was decommissioned on April 1, 1975.
The main marine radio beacon group covering the North East Coast comprised Souter Lighthouse (call letters, SJ), Flamborough Head Lighthouse (FB), Longstone Lighthouse (LT) and Fife Ness Lighthouse (FP). All transmitted on the common frequency of 303.4 KHz.
Souter Lighthouse also provided a radio beacon calibration service, transmitting Morse identification letters, PT.
In 1955, when the port’s radio beacon was introduced, certain navigation signals and marks were quite different from those in use today.
For instance, the can buoy marking the unfinished end of New South Pier was painted in black and white vertical stripes, while a bell on the Old North Pier was sounded for 30 seconds every minute during foggy conditions.
To warn of danger in the harbour, two black balls would be exhibited on a horizontal staff from the Pilot Station during daytime, while at night, a green light was shone from the upper window of the pilot house.
During the day, vessels were permitted to enter South Docks when a flags were flown at half-mast from the root of the old South Pier and at No. 3 Gateway dock entrance. Flags would be flown at mast-head to indicate it was safe to proceed outwards.