At the height of analogue television, how much spectrum bandwidth was allocated to the magic rectangle?
Radio frequencies are precious natural resources. There are only so many to go around. Now, it is true that, in many cases, frequencies are reusable (e.g. a tv station in Glasgow can be on the same frequency as a transmitter in London, without causing mutual interference), but frequency bands are generally given over to one or two uses each.
So how much spectrum is taken up by one use: broadcast television to households? When I was younger, and we had only a few television channels, big programmes in the UK would routinely attract 17 million viewers, or thereabouts. One night in 1990, when I appeared on the popular consumer report programme “That’s Life” playing a telephone accompanied by the musically-talented Howard Leader on accordion, the figures that evening indicated that 11 million people tuned in to view. How much of that valuable radio-frequency spectrum did television occupy?
A simple answer is to add together the bandwidth taken up by the four bands used for television broadcasting in Europe, called Bands I, III, IV and V.
Their total bandwidth? 471MHz.
When I was younger, no radio frequency above 1GHz really mattered to the average consumer at home. So, until the advent of PCN mobile telephones in 1995, up at about 1.8GHz, the range of spectrum occupied by broadcast television was very nearly one half of all radio frequencies. Everything else, including all radio, ship-to-shore messages, radio amateurs, weather services, early cellphones, time signals, radio teleprinters, was in the other half.
With the advent of satellite broadcasting, the usable spectrum has expanded; but so has the use of television. All that precious bandwidth, used for entertainment, news and education? Still roughly half.
That’s either a disappointment, or a great responsibility.