History
Chillerton Down did not form part of the main Post Office microwave network but features on the 1959 Network map as an "existing" site linked to Southampton. This was to provide a feed for the Southern Television transmitter which entered service in August 1958. The "network" programme was sent from London (Museum) to Rowridge, via Golden Pot, as for the earlier BBC television link, and from there by cable to Chillerton Down. A 2 GHz link to the main exchange at Southampton and further cabling completed the link to the "Plaza" studios where local programming and advertisments were added before sending the desired output back to the transmitter. (When Southern's other main transmitter at Dover entered service in 1960 the programme feed continued via cable to Rowridge and then the SHF link back to London.)
Rowridge developed as a Post Office SHF site, independent from the BBC transmitter but operations at Chillerton Down ceased in the late 1960s when the television distribution network between London, Southampton and Rowridge was re-organised and converted to 625-line standard. The required conversion to 405-lines for the VHF service from Chillerton Down is likely to have been carried out on-site, using the UHF signal from Rowridge.
Chillerton Down was, however, used for a second time in the 1980s, providing a telephony link to the Channel Islands. Graeme Marett, author of Connecting Jersey has provided the following background: "The IOW project was started because of an unprecedented failure of all submarine cables to the UK from the Channel Islands, not once or twice but three times in a short period of time in the late 70s and early 80s. The resulting disruption to the local finance industry was so great that it was decided to create a back-up route via microwave. The existing inter-island link was increased in size and studies were undertaken on the feasibility of an Alderney - IOW link. Both Guernsey and Jersey telecom departments were involved and the costs shared with the PO under the agreement signed at the time of the local States departments purchase of Post Office equipment on the islands in 1971.
Work on this system started by Post Office Telecoms using "stock" equipment at the end of 1980 and it was commissioned at the end of 1981. It had both space and frequency diversity systems built in to make it more robust. It was a 960 channel system that used diversity switching since it was over a considerable distance. The quality of the link was indifferent since it was subject to the vagaries of the weather and was likely to be unusable altogether at spring tides since it was barely line-of-sight. However, it carried analogue circuits and thus was able to sustain a level of service albeit of poor quality.
As far as I am aware it was only used once in earnest (around 1983/4) and never carried any permanent traffic. It was later abandoned when more capacity was available on the CI - France link and the sinking of the first fibre submarine cable which was given more protection against dragging anchors in the Channel."
