Relay race 

10 November 2014 tbs.pm/5695

Compare and contrast the two maps above and you’ll see the big differences between VHF Band-I and UHF broadcasting.

On the 1950s colour map, the single VHF channel 2 transmitter high up on Holme Moss can be watched from Hartlepool to Welshpool and the Lake District to the Wash. Winter Hill, one of the UHF transmitters designed to replace it, is shown on the second map. It misses swathes of populated areas, including much of riverside Liverpool. It also requires 20 relay stations, by this point in 1974, to adequately cover important towns like Lancaster, Todmorden (where Transdiffusion was based at the time this map was published) and Bacup.

Note also the difference in aerial advice: on the VHF map, there isn’t any. In fringe or difficult areas, a properly mounted and pointed VHF aerial was required for a good picture. For most people, however, satisfactory results could be got from just having an aerial.

By the time of UHF, the type of aerial, its placement and its polarity are all very important. A professional installer is required or else the picture quality will range from rubbish to not very good.

Also worth noting, on the third page, is how the frequencies for what would later be called Channel Four have already been assigned. What UHF had over VHF was bandwidth: more lines, colour pictures (although both are possible on VHF, of course) and room for four services rather than just two as VHF provided. Planned in advance for 4 channels, UHF also provided something VHF had never done with BBC1 or ITV: almost complete national coverage for the new Channel 4 from day one.

A Transdiffusion Presentation

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1 response to this article

Ben Grabham 19 November 2014 at 12:42 pm

Certainly when I was living in France in the early 2000’s there was still colour tv on VHF – although most people had by then switched to one of the two main satellite providers

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