History
Thrumster is one of the first true microwave link stations set up by the Post Office for general telephony purposes. The link to Braewynner entered service in 1956 on 4 GHz using equipment to a PO design (type RS 10/2) and carrying 240 circuits. The scheme was designed to integrate with existing cable at either end and many of the technical developments for the Braeywynner/Thrumster link were adopted as standard practice. BT Archives has a number of papers covering the technical detail and the operational performance of the link.
The link consisted of a single "hop" which was for its time over a relatively long distance and across water. Various "diversity" arrangements were adopted to ensure consistent performance. Guyed masts of the standard type - square section with "pointy top" were used at both ends of the link - the one at Thrumster survives.
A further route was added from Thrumster to Wideford Hill, via Olrig Hill, with similar parameters but using equipment manufactured by STC (type RL4B) which was designated RS 10/3. The antennas for this link were carried on relatively short self-supporting towers.
From 1958 Thrumster was used by the BBC for 405-line television broadcasts, with FM radio added in 1960. The transmitting antennas were carried on the Post Office mast but the receive antennas were on smaller structures - the television service was received off-air from the Meldrum transmitter (adjacent to the Post Office Core Hill site) as there was no SHF link available for television purposes. The television transmitter closed in 1983 and the radio services moved to another site in 1984.
The route from Braywynner remained in service until around 1978 by which time a replacement running from Tor Sliasg running along the coast via Helmsdale was in full operation. It appears this route may have been retained to provide a link towards Orkney and Shetland with "big dishes" still present in 2016 and the 60 year old mast a contender for the longest-serving structure in the PO/BT network.