24 February 1994
Norman McLeod
I had not intended to tackle the 105-108 issue for a week or two yet: it'll take a while for the Radio Authority's paper to sink fully into my consciousness, and besides, we have until nearly the end of April to put our submissions in.
But Mark Thomas's letter in Issue 98 raises a broader point which I sometimes overlook, but which is striking in its implications.
I have the benefit, like many radio enthusiasts, of a high-quality tuner connected to an outdoor antenna. Across the local radio sub-bands, I can reliably receive sixteen different transmitters, nine between 94.6 and 97.6 MHz, and seven between 102 and 105 MHz. Admittedly between them there are only ten different programmes, there being four transmitters carrying identical BBC local radio programming, three for Southern FM, and two for Radio Mercury.
But officially I have been reminded that (God Forbid) I am only supposed to be listening to two services - BBC Radio Sussex-and- Surrey and Southern FM. Indeed, for your average punter with a clock radio in a basement flat, that is all he or she will be able to get apart from the national networks unless an RSL comes along. I can well understand the lack of appeal radio has for many of my friends when I realise how little choice it has to offer them unless they invest in a serious receiving installation.
What is being admitted is that in a total of six megahertz of spectrum, only two services are being officially provided to most of the population. Further, most of the options for 105 - 108 MHz promise only one more service in another three megahertz of dial space. Can this be right? Is eight services across twenty megahertz the limit?
A load of balls
The situation is like a rectangular tank filled to the brim with round balls of various sizes above a certain minimum. Ostensibly the tank is full, in that if the lid is put on the balls reach right to the top. But in fact there is room for more balls to be put into the tank if the minimum size is reduced. Little balls can slide around the interstices between larger ones, so that the total capacity of the tank increases if the minimum ball size is lowered.
This is the situation, not in the as- yet unexploited 105 - 108 MHz band, but in much of the network and local radio sub-bands used right now. For instance, the BBC's national network transmissions appear to sterilise 2.2 MHz worth of spectrum for each service - a strong argument for moving them off FM and onto DAB if and when that service reaches a majority audience.
But usually there is just one major transmitter responsible for the service to a particular community, and so only that transmitter needs to be protected from interference. Low-power transmitters occupying the frequency of out-of-area major network transmitters will deprive no-one of the wanted network service and can be planned not to interfere with the distant transmitter inside its own coverage area by virtue of the imbalance of powers.
Similarly, in the local radio sub- band, if only two services can be expected across two sub-bands each three megahertz wide, then only those two need to be protected against incoming interference, and there is some scope for new stations of at least RSL levels of substance to run co- channel with out-of-area stations.
So, as an aside to the whole 105- 108 debate, I would submit that claims that all existing spectrum is fully saturated are exaggerated.
Any readers wishing to comment on what I have said are welcome to call me on 01 273 684 172 or send e-mail to normac@fastnet.co.uk
Copyright NJ McLeod 1995