Site Records

SiteName: North Weald - Ongar Radio Transmitting Station

North Weald Bassett
OS Grid Ref: TL506040

Sub Brit site visit August 1996

[Source: Nick Catford]

Ongar Radio Transmitting Station occupied a site of 730 acres at North Weald in West Essex adjacent to the late 19th Century North Weald Redoubt, one of 13 London Mobilisation Centres.

Photo:One of the transmitter halls at Ongar
Photo by Nick Catford

It was originally built in 1920 and operated by Marconi's Wireless Telegraph Company. In September 1929, control passed to Imperial and International Communications when the telegraphic communications of the Empire were placed in the hands of a single operating company. The name of the company was changed to Cable and Wireless in June 1934 and the company owned the radio station until the passing of the Commonwealth Telegraphs Act, 1949, whereby the United Kingdom radio services of the Post Office and Cable and Wireless Ltd. became integrated on April 1st 1950. Ongar Radio was one of three pairs of transmitting stations, each pair consisting of a transmitter and receiver station; Ongar being paired with Brentwood.

These dates have figured prominently in the stations affairs, nevertheless traffic continued to flow steadily despite the vicissitudes of transition and the changes in stationary

'C' Station short wave hall showing HT rectifiers and switchgear on the gallery, C6 40kW short wave transmitter on the right and control tables in the centre of the hall

The original scheme was for a short wave beam station with four transmitters housed in three buildings, two in 'A' station, one in 'B' station, one in 'C' station plus a power house with three Vickers-Petters diesel engines coupled to DC generators. The A B & C stations and the power house were separated from each other by up to half a mile.

The first radio-telegraphic services from Ongar in 1921 connected London with Paris and Berne using Morse code. The transmitters were designed to operate simultaneously from 'A' station and the signals were mixed and radiated from one aerial on two different frequencies.

Photo:Ongar Radio Buildings - the right hand building later became an engine generator test centre
Photo by Nick Catford

The first short wave transmitters installed at Ongar were GLS and GLQ known as Gee London Sugar and Gee London Queenie, both rated at about 6kW. They were installed in 1924, adjacent to the 'C' station building and radiated from single harmonic aerials; just pieces of vertical wire of no specific length.. The 'C' station short wave transmitter hall was completed in 1931 when five SWB 1 (Short Wave Beam) transmitters were installed. The Morse signals came down the line from Radio House (the Marconi station in London) where the operators punched out the messages and amplifiers at Ongar stepped up the voltages until the full radiated power of the transmitters was chopped into dashes and dots. The beam wireless picturegram service opened between London and Melbourne in 1934 with the transmission of facsimiles being added to Ongar's functions.

There was a programme of continual progression at Ongar, two new 120kW long wave transmitters were installed and the gaps in the short wave building were gradually filled with more transmitters. During 1939 and 1940 the original SWB 1's were converted for cooling by water instead of oil to reduce the risk of fire by incendiary bombs.

Photo:Transmitter Hall - three quarters of a mile from the main site
Photo by Nick Catford

With the closing down of the Tetney Transmitting Station in 1943 a further concentration of the Cable & Wireless services was brought about by re-erecting the Tetney masts and beam aerials at Ongar. These were fed from a new building known as 'D' station, three quarters of a mile from the main station. This was the first transmitting station in the country to run completely unattended except for visits from maintenance staff. Four 25kW short wave transmitters were installed to take over the services to Bombay, Melbourne and Moscow while a fifth 20kW transmitter known as 'D1', of an advanced design, communicated with Cairo and the Middle East.

With the completion of 'D' station in 1944 another building to be known as 'E' station was under construction for further expansion of the telegraphic services. This was located on the south side of the Epping - Ongar railway line and no aerials were allowed to cross the line. It was designed for six transmitters of the SWB 8/10 type feeding a self-contained group of rhombic aerials.

It was common practice for 26 of the 31 transmitters at Ongar to be radiating simultaneously during peak traffic periods in the afternoon and evening. This represented a load of over 800kW from the power supply and 280kW of radiated energy.

Further information and pictures about this site continues here

[Source: Nick Catford]

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