ITV 405 line VHF TV TRANSMITTERS
|Channel / Polarisation||9 H|
|Max. Vision ERP||10 kW|
|Site ASL||328 ft|
|Aerial ASL||753 ft|
Studies showed that the only Band III channel which could be used to cover the islands without causing harmful interference in the service areas of several French stations was Channel 9, horizontally polarised, and even with this channel it would be necessary to restrict the power radiated towards the French coast to about 1 kW. Accordingly, it was necessary to site the transmitting station on the north coast of Jersey, where 1 kW was just enough to serve that island, and to beam a higher power, 10 kW, across the sea to Guernsey which lies 25 miles away towards the English mainland.
The supply of mainland programmes to the Jersey station for rebroadcasting in the islands presented unusual problems because Stockland Hill, the nearest mainland transmitting station, used Channel 9, the same channel as Fremont Point, the Jersey station. The solution adopted was to install on the small island of Alderney an 'off the air' receiving station using diversity reception techniques to pick up the Channel 9 vertically polarised transmission from Stockland Hill 80 miles away and to pass it over a multichannel microwave link to Fremont Point. The overseas path length of the microwave circuit is about 40 miles. To ensure that the Stockland Hill signal could be received in Alderney without interference from Fremont Point, the power radiated by Fremont Point towards Alderney on the same channel had to be restricted to the low value of 200 watts. Fortunately many people in Alderney are able, with good aerials and receivers, to view directly if somewhat inconsistently the transmissions from Chillerton Down on Channel 11.
There were many complications in this apparently simple vision link scheme. The distance is such that the changing propagation conditions over the sea path involved caused wide fluctuations in the strength of the signals received in Alderney from Stockland Hill, and for a small proportion of the time these signals may be unusable for rebroadcasting from Fremont Point. On these occasions it was often possible to make use of the reception of Chillerton Down in Alderney to supply the programme and this was also done on those occasions when the required programme was not available from Stockland Hill. Yet another procedure sometimes most useful under certain conditions of propagation is the direct reception and rebroadcasting at Fremont Point of transmissions from the Caradon Hill transmitter on Channel 12.
The programme service from Fremont Point began on 1st September 1962.
IEE report about the 405-line rebroadcast link arrangement at Alderney