(4 June 1995)
Norman McLeod
I noted the comments of Greg
Bance in Issue 112 (p 14) [RADIO MAGAZINE?]
concerning frequency assignments.
This is what he said:
"...the fact about frequencies is
that there are enough of them -
certainly on AM - to share out
among all who wish to operate a
radio station...for example, on 1278
kHz, 1017 kHz and 765 kHz, there
is only one UK broadcaster apiece;
yet several metropolitan stations
are crammed onto 1458 and 1152
kHz."
Well, Greg, there is in fact a BIG difference between 1458 and 1152 kHz and the other channels you mentioned, and the fact that you don't recognise this difference weakens your argument.
If you have an old radio with a dial marked in metres produced between about 1950 and 1970, then you will quite likely find the following stations marked on it:
Third: 464m
North: 434m
Scottish: 371m
Welsh: 341m
London: 330m
West: 285m
Midland: 276m
North: 261m
Light: 247m
N Ireland: 224m
West: 206m
Third: 194m
These twelve wavelengths were UK landmarks then, and are still with us today. Together with the external services transmissions on 1296 kHz, they emerge today as the ONLY channels where the UK has a high-power international allocation capable of fitting in high- power regional or national network services. The old regional Home Service variations vanished in the early seventies, and there was a further major reshuffle in 1978.
Today the pack emerges like this:
World Service: 648 kHz (was 464m)
Radio 5 live : 693 kHz (was 434m)
R Scotland : 810 kHz (was 371m)
R Wales : 882 kHz (was 341m)
Radio 5 live : 909 kHz (was 330m)
Radio 1 : 1053 kHz (was 285m)
Radio 1 : 1089 kHz (was 275m)
Misc ILR : 1152 kHz (was 261m)
Virgin : 1215 kHz (was 247m)
Radio Ulster : 1341 kHz (was 224m)
Misc ILR/BBC : 1458 kHz (was 206m)
Misc ILR/BBC : 1548 kHz (was 194m)
You can see that the frequencies of 1152, 1458 and 1548 kHz, originally 261, 206 and 194 metres, are high-power channels reassigned to so-called local radio, but still used by high power transmitters. The London services on these channels burn 25, 50 and 100 kW EMRP respectively.
All other frequencies, with the exception of 1485, 1584 and 1602 kHz, are assigned to some other country for high power use, and can only be used in the UK by stations of a sufficiently low power (no more than 1 or 2 kW) not to cause interference to the foreign service.
The three exceptions mentioned above are universal Europe-wide low-power channels for 1 or 2 kW transmitters with no high-power assignments anywhere. This doesn't always make them much quieter at night, as the number of transmitters in use is quite high.
To cover London well needs a transmitter capable of at least, say, 2mV/m field strength 50km away. The amount of power necessary is little more than 1 kW at the very bottom of the dial (where Spectrum is fortunate to find itself) but rises rapidly to around 5 kW about 800 kHz, 20 kW just above 1 MHz and as much as 100 kW at the top of the dial. It's not easy to serve London in one go without using up a high-power UK channel...
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