THE TRANSMISSION GALLERY
TALES FROM A COLD FIELD
Being fairy-stories told to the author as a young engineer
© Ray Cooper, 2005 (2nd revised edition, Jan 2006)
"In eighteen months, medium-wave broadcasting will be dead..."
Well, that was one remark passed when FM broadcasting started in earnest. Like many such comments it perhaps contained an element of wishful thinking: most of the medium-wave transmitting stations were pre-war and needed refurbishing if not downright re-engineering: why not replace it all with modern FM stuff? Automatic gear, much more efficient, no large aerial arrays to blow down....
With hindsight of course one can see why it didn't happen. The 'transistor portable' boom that effectively saved medium wave had not then started. FM wasn't much use for the car radios of that period. Consumer resistance to rushing out and spending good money on a new receiver had never been higher. The early FM sets were not easy to tune, compared with their MW counterparts.
So FM in those days was a minority sport, indulged in only by those who couldn't bear to listen to the cacophony that the medium-wave band was becoming during the evening.
At this time, the Sutton buildings were subjected to a massive expansion. A new FM hall was built in the space between the building and mast, and a new massive 'Band III' hall alongside it. In those pre-ITV days, it was felt that when the second BBC TV service came along, Band III was where it would be going. Wrong, of course. The hall stayed empty, apart from junk storage, until BBC 2 came along in the 'sixties. However if you looked carefully at the lighting supply switch and fuse boards, you would see items labelled 'Band III Hall' even as late as the 'nineties.
This expansion explains one or two architectural oddities about the building interior - for example, if you walk along a certain interior corridor you will see, on one wall, bricked-up exterior windows, complete with windowsills and drips.
The FM Transmitters
The new transmitters were supplied by S.T. & C. and were, in some respects, eccentric devices and so fitting in fairly well with the ethos of the site. It was a parallel-pair installation: two transmitters per service, nominally 10kW per transmitter, and in those days of course labelled 'Home', 'Light' and 'Third'.
One transmitter for a service was combined with the corresponding units for the other services, and fed to one-half of the aerial array. The other units had their own separate combiner feeding the other half of the array. The system thus had redundancy, a transmitter could fail and the remaining unit would carry the service, albeit at reduced power (quarter power, in fact: half the transmitter power was lost, as well as half of the aerial gain).
The transmitters were originally specified for unattended operation, but never proved to be quite reliable enough for that: the best that was achieved was a period quaintly known as the 'UGH' (UnGuarded Hour) which ran for the short period during which programmes were still being broadcast and there was no staff presence (some programmes could start at 7 a.m. - other might run until 1 a.m.) During these periods, transmitters were run by remote control from a staffed Medium-wave site - Droitwich, in the case of Sutton. There was only limited control; units could be switched off if misbehaving, or programme feeds or drives could be changed over. It was accepted that anything in the nature of a major fault would simply have to wait until the shift staff arrived at 08:00 before being rectified.
The Coming of Stereo >