SR B70 SHF Radio-Relay Set - A Potted History

By Archie Cairns 260 Signal Squadron (SAM)

Royal Signals Association

 

 

The SR B70 was designed in the 1940's by G H Barker (known as Tubby to his friends) and is believed to have been manufactured by Plessey. I have not been able to establish exactly when the set first came into use but it was probably brought into service with the Corps in the early 1950's. It was certainly in use in 1957 when His Royal Highness the Duke of Edinburgh visited Catterick and inspected the young trainee National Servicemen who were receiving instruction on the set.

 

The man-portable SHF radio-relay set using wideband FM for multichannel modulation, bandwidth 60 kHz and above, using 14 channels at 20 MHz spacing or able to use 5 MHz spacing with a wavemeter.

Powered by an AC supply at 110 to 250V and consuming 125W. With an RF output of 0.3W the sets had twin 16" antennas in parabolic arrangements and give a range of 15 to 25 miles (24 to 40 km) or with two stations could reach up to 60 miles.

 

Main unit and power unit are each 20.5 x 15.5 x 10 inches and each weigh 50 lb. Separate System Control Box measuring 8.5 x 9.5 x 12.5 inches and weighs 22 lb 8 oz enabled the Radio Relayman to connect a field telephone and to speak over an engineering channel to his opposite number at the distant location. The whole station weighs 150 lb.

 

The set was mainly used mounted on a tripod but could be mounted on a telephone pole or large tree with a special clamp designed for this purpose. In the users handbook an artist impression shows the set mounted on a 40-foot mast with guy ropes, which would have presented the operator no end of problems as he struggled to climb the mast to establish communications. The early pioneers quickly found a solution to the height problem with the purchase of two builder's Zip Up Towers.

 

A modified version for use with Thunderbird Surface to Air Missile Systems handles up to 140 kilobits/second. Although described in the documentation as being "manportable" I can assure you, as a former Radio Relayman, you wouldn't want to carry this load very far.

 

As a standalone unit the SR B70 with its narrow 'line of site' signal provided a secure point to point radio relay voice link. However following Trials at SRDE and in the field with 260 Signal Squadron (Trials) which was based here in Blandford, a Radio Relay System was developed at SRDE by a team lead by Stan Davies using Multiplex Channel Equipment and Line Equipment enabling telephone and data communications to be passed from one subscriber to another, thus dispensing with the need to lay miles & miles of multiple cables which were vulnerable to weather conditions, accidental damage and enemy action.  This small transceiver played a vital role in providing communications for the Royal Artillery's latest weapon of the day the English Electric Thunderbird II Missile enabling a superior Air Defence cover for the British Army of the Rhine during the Cold War.

 

The set was probably first deployed in this role in 1961 when 36 Heavy Guided Weapons Regiment RA was sent to Germany to reinforce the British Army of the Rhine with a troop from 217 Signal Squadron following the construction of the Berlin Wall.  Following trials with other more modern radio-relay and the radar equipment used by the Surface to Air Missile the SR B70 proved to be more efficient at handling the data. The SR B70 remained in this role up until 1977 when the Thunderbird Missile System became obsolete. The unit responsible for providing the communications for the Thunderbird Missile was 260 Signal Squadron (SAM) based in Dortmund Germany and formed part of 36 Heavy Air Defence Regiment Royal Artillery.

 

The B70 also saw service in Northern Ireland with 233 Signal Squadron the unit deployed a radio relay link across the rooftops in Belfast in February 1976. So don't be surprised if you are asked to use the SR B70  at some point in the future. The set was in the Museum when I joined the Corps in 1968.

 

This was the beginning of a new dawn in telecommunications laying the foundations for modern mobile telephone and data communications that we are all familiar with today.