Cold War Sites

GPO PR1 Protected Repeater Station

  Created 21-10-2001   Last update 28-10-2012

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The Requirement
A series of government reports circulated in the early and mid 1950s highlighted the fragility of Britain's existing telephone network as the weakest element in her nuclear defence system. Both government defence communications and communications between remote stations and operations’ centres on the newly developed ROTOR radar system depended upon this network of vulnerable, pre-war landline cables. Most of these trunk cables passed through the centres of large cities which would be likely targets in a nuclear attack. To partially rectify this situation new diversionary cables were laid to circumvent the target areas and new ‘bomb-proof’ semi-underground repeater stations were built at the nodes of this new system.

These stations were known as ‘GPO Protected Repeater Stations’. The purpose of any telephone repeater station is to boost the strength of the electrical telephone signal to counteract the losses that have been incurred in the wires through which the signal has travelled. These ‘protected’ stations were different to standard repeater stations in that they were specifically designed to continue operating in the event of nuclear war and were often referred to as ‘hardened stations’. They would carry essential war related traffic so that defence, recuperation and retaliation could be maintained.

Only eight of these stations were ever built and they came in two varieties: PR1 and PR2. The only difference between them is that the PR1 equipment rooms are about 20 feet shorter than the PR2.
They were located at:
 
  • PR1 Lyndon Green - Birmingham
  • PR1 Portsdown - Portsmouth
  • PR1 Queslett - Birmingham
  • PR1 Stockport - Manchester
  • PR1 Swinton - Manchester
  • PR1 Uddingston - Glasgow
  • PR2 Rothwell Haigh - Leeds
  • PR2 Warmley - Bristol
Station Protection
The term ‘protected’ or ‘hardened’ is open to some interpretation in this instance. The stations were designed in 1951; one year before the first nuclear fusion weapon (H-bomb) was tested and were thus intended to withstand the more sedate fission weapon (A-bomb) of that era. For instance the first A-bomb (1945) had a yield of 20 kilotons (thousands of tons of TNT) whereas the first H-bomb (1952) yielded 10 megatons (millions of tons of TNT). The station had a ground floor and a single underground basement level. It was fitted internally with not too substantial blast doors and had its own power and air filtration systems. When compared to nuclear bunkers in the USA or USSR it can be seen that the word ‘protected’ has been used here in its lightest sense. This was fairly typical for UK nuclear protection as a whole.

Another factor which needs to be taken into consideration is that early on in the Cold War a limited nuclear conflict was considered to be a likely possibility not least because there were only a restricted amount of fission weapons available. Hence the amount of protection given to any hardened structure need not be extreme. However, once the MAD (Mutually Assured Destruction) scenario arrived due to the proliferation of high yield thermonuclear weapons, hardening to any degree began to look unconvincing.
 

Portsmouth Map Of Nuclear Strike

The map on the floor shows Portsmouth (Portsea Island) and the spread of a nuclear detonation. The epicentre is at the junction of Lake Road and Fratton Road; 1 mile east of Her Majesty's Naval Base Portsmouth. The solid circle is 3/4 mile across and the outer ring 2 miles. The PR1 station at Portsdown is under the blackboard top right.

 
The Layout
As has been stated the station consisted of a ground floor (above surface) and a single level basement. The distribution of the equipment within these floors does not appear to follow any logical design. For instance the most vulnerable part of the building was the ground floor and yet this contained equipment that was vital to the functioning of the station. The building was divided into three distinct sections: 1) Office section 2) Ground floor protected area 3) Basement protected area. The layout was approximately as follows:
 

Ground Floor

  • Battery Room
  • Main Distribution Frame (MDF)
  • Repeater Racks (PRE/51)??
  • Manual Telephone Switchboard
  • Repair Area
  • Valve Store
  • Motor Generator Sets
  • Air Intake, Filtering and Distribution
  • Crane Shaft
  • Emergency Exit with Chicane

Basement
  • Diesel Generators
  • Transformers
  • Air Filtration Plant
  • HV Electrical Switchgear with CO2 fire suppression
  • Cable Glands – for the comms cables
  • Repeater Racks (PRE/51)??
  • Air Compressors
  • Emergency Exit with Ladder to Surface
     

There was no provision for personnel accommodation such as sleeping and shower facilities in the protected area.

Electrical Provision
Since the stations were built before the era of solid state electronics, such as transistors and microchips, thermionic valves (usually referred to as just ‘valves’) were used in the circuitry. These consumed a considerable amount of power even when on standby and emitted a significant amount of heat. Consequently a generous power plant was required just to power-up and cool the electronics. Because the stations had to operate under wartime conditions they were self sufficient in this respect having two diesel powered 3-phase AC generators. One of these was a 215 kVA unit supplying the DC power via motor generator sets and the telecommunications load. The other 250 kVA unit served the environmental requirements of the station such as air-conditioning and lighting. Given the size of the station the versatility of the power distribution system was quite sophisticated. Once power from the national grid was lost emergency lead-acid batteries took over until one of the diesels auto-started using compressed air from a pressure vessel. The underground fuel tanks contained enough diesel to last four weeks.

 

The End

The entire interior of the Portsdown PR1 station was stripped out and sold for scrap during March 2011. The empty shell is now boarded-up.

 

 

 Grid Ref SU663066

Google Earth Aerial View

Visit this site - Portsdown Walk No1

What is a Repeater Station?

 
Sources: Nick McCamley
  Subbrit
  Anon
  Brian Wells
  Jeff
 

 

 
 Portsdown PR1 Nov 2012

The GPO PR1 hardened repeater station. It sits on the northern slope of Portsdown, a location possibly chosen to give it some blast protection from a nuclear strike on the city of Portsmouth to the south. This photo, taken during November 2012, shows how the building is deteriorating. The white paint is flaking, and much of the roof is covered in standing water.

 
 
 
Main Entrance

The main entrance with a panel depicting the year of building:1953.

 
 

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