History

The London - Southampton route is included on a 1959 map as "Planned (sites not yet determined)" however it appears two intermediate sites were intended. This choice may have been influenced by experience with the earlier London - Isle of Wight TV link. The route would serve as a more suitable replacement, with the potential to carry telephone traffic.

The plans progressed, slowly, during the 1960s. The original intention seems to have been for the route to become available with the new London Post Office Tower. All sites were new: ultimately delays in completion at Bagshot delayed the opening of the route. At Butser Hill the Post Office built a tower of one-off design adjacent to a radar link site operated by the Ministry of Civil Aviation (this would tranfer to the new tower). The Southampton terminal was at Thornhill, approximately four miles east of the city centre, where an existing repeater station allowed access to trunk cables. Original plans would have used a "Standard Tower" at all sites (except London and Rowridge) but it seems Butser Hill was the subject of further negotiation. The standard design of building was used at all intermediate sites.

Contract 23542 was awarded to GEC in November 1962 at an agreed price of 151,882 for a (lower) 6 GHz system. This had risen to a final cost of 260,257 by March 1966 and covered the London - Southampton section only. The extension to Rowridge was part of Contract 23562, awarded in December 1963, for a 2 GHz system along with "moving of control point to Western Esplanade (Soutampton). The original price of 40,968 had risen to 88,117 by June 1966. STC and Marconi had both been invited to tender but were unable to meet the specifications and did not bid. The target date for the main section is not known but the Rowridge section was to be completed by "1st April 1965 subject to receipt of full and final engineering information by 1st March 1964". Two further contracts were awarded: 23581 62,538 in August 1964 (66,096 at April 1966) and 300517 in August 1966 (25,000), both for "additional channels". Completion dates requested were 1 March 1968 and 1 July 1968 respectively. It is unclear whether these additions related to 625-line televisision (BBC2 was available from Rowridge, using temporary arrangemets, from January 1966 but BBC1 and ITV were not available until December 1969). There does not appear to have been a supplementary contract for the Southampton - Rowridge section. It is also possible the additions related to initial telephony provision.

The main section used horn antennas, a design which was intended to be suitable for operation on 4 GHz and potentially on other bands. The extension to the Rowridge television transmitter on the Isle of Wight was provided from Thornhill, the "doubling back" required to link with the studios at Southampton was now via cable. A local Television Network Switching Centre (TVNSC) was estalished at the central repeater station which was under construction in the mid-1960s at Western Esplanade. Thornhill would be unattended. The distance between Thornhill and the TVNSC is relatively short but cables ran via an (existing) intermediate repeater station at Bitterne (SO/D) located at Garfield Road.

A 1977 network diagram for the TVNSC shows three "vision circuits" from London to Thornhill and two in the reverse direction. One incoming circuit was connected directly to Rowridge - assumed to be for BBC2. The other two were routed from the NSC to BBC and ITV studios. Two of the circuits to London were connected to outputs from the Southern Television studio: one to feed their Dover transmitter, the other to allow contributions to "Network". Switching at the TVNSC was provided for "make good" purposes, it seems normally the circuit configuration was static. Programmes for BBC1 and ITV were sent to Rowridge via cable to Thornhill. The 1986 revision of the network diagram shows the addition of three more circuits from London. One was routed directly to Rowridge for BBC FM distribution, another to the ITV studio for Channel 4. The BBC2 feed was now routed via the Southampton studio. A further inbound circuit labelled as using "temporary" eqiupment also routed to the ITV studio - possibly this was to allow the TVS studios at Maidstone to be treated as an "outside source". One return circuit to London had been added, this would seem to be the Channel 4 transmitter feed for Dover. A switching matrix had been added at the TVNSC to allow the ITV studio to be bypassed and the Rowridge (and Dover) transmitters fed directly with the TV-am output from London.

Little is known of the telephony usage over this link, however a document giving estimates of expenditure for the period 1966 to 1970 indicates plans for a system with 1800 circuits (plus "protection channel") had been approved by 1966 at an estimated cost of £130,000. A further £30,000 was estimated for a further 1800 circuits ("Radio Link G" - it is not currently known whether links A to F included the vision circuits or perhaps related to trunk cables). The high cost of the initial work suggests the telephony provision may have used a different band, perhaps requiring new antennas. By the 1970s there were at least two radio systems in operation, possibly the original equipment was unable to support the requirement for 1800 circuits per channel.

Subsequent development would be driven in the 1970s by growth in telephony and in the 1980s by plans for a digital network. The overall capacity of the Southampton route was constrained by the shared section between London and Bagshot which also served the route to Bristol (and beyond). Peak demand for vision circuits would have been in the mid-1980s. Channel 4 moved to a digital (fibre) distribution network on 1 January 1993. The ITV franchise passed from TVS to Meridian on the same date and the new company was an early adopter of digital links. The BBC migrated to digital links provided by Energis in January 1995. The System X digital network was planned with main switching units (DMSU) at Portsmouth and Salisbury - not Southampton. Maps showing plans for the digital trunk network usually omit the London - Southampton route, however Southampton - Rowridge was included on some versions.

A photo of Bagshot in 2006 shows no dishes facing Butser Hill yet they remained in place for London - Bristol. This suggests the Southampton route closed earlier than other parts of the network. A photo of Butser Hill in 1999 shows only two large dishes remaining (of a 1970s design) which appears to confirm digital links were never installed on the London - Southampton route. Planning documents show a "south coast" route had been planned for the 1980s which would have used Thornhill and Butser Hill together with new sites near Salisbury and Goodwood. These were never built (though BT may have shared existing structures instead) and there little evidence the route was ever operational. More information would be welcomed.

To be added: contract details.