History

For historical reasons the "missing link" between Bristol (Purdown) and Cardiff (Wenallt) was a relatively late addition to the Post Office network. Bristol - Exeter developed originally for ITV links but 405-line vision circuits between London and Bristol were carried via cable, as was the continuation to Cardiff. West of Cardiff, SHF links were provided for BBC and ITV transmitters. It was the requirement for links to 625-line standards which led to the introduction of SHF between London and Bristol, extended to Cardiff.

Documentation of the contract details is incomplete, however the systems were planned as "Bristol - Cardiff TV Radio Link: (BBC Welsh Program and BBC2)" and "Bristol - Cardiff Radio Link (960 circuits)". The former system was described further as "The provision of two operational channels and one protection channel in the Bristol - Cardiff direction and one operational channel and one protection channel in the Cardiff - Bristol direction. Also the provision of temporary channel in the Bristol - Cardiff direction, pending completion of the permanent provision". BBC2 entered service at the Wenvoe transmitter in September 1965, therefore it can be assumed the temporary provision (at least) was operational by this stage.

The initial telephony provision was stated as "The addition of two two-way working channels to the existing radio system...". The specification of 960-circuit systems suggests it was acceptable to use GEC's first-generation L6 GHz equipment (perhaps redeployed from another route). Contract 300525, awarded in November 1966, may relate to the telephony work. The low value of £22,206 perhaps reflects the incremental cost of adding two channels at two sites.

By the mid-late 1960s it was policy not to use horn antennas for new links and it appears Wenallt only carried one horn, for the original TV links west of Cardiff. At Purdown there is similarly no evidence of a horn antenna being installed for the link to Cardiff, however the height of the tower was increased with a dish facing Wenallt installed at the top of the new section.

By 1984, vision circuits had been installed for all four television channels, plus BBC FM distribution, with one circiuit in the direction Cardiff - Bristol for BBC purposes and two for ITV (this may relate to HTV having studios in both cities). A large number of "protection circuits" was available between Purdown and Wenallt, suggesting systems operated in multiple bands - this may indicate significant expansion in the telephony provision. Bristol - Cardiff was included in the 1980s development of 11 GHz digital links for System X.

Photos suggest the main dishes were removed from Purdown in 2009.