Now BBC Radio Ulster on 1341 kHz - still from the diamond shaped Blaw-Knox radiator at Lisnagarvey. I believe it to be the only example of such a radiator in the UK & Ireland.
Thanks, David. We should be grateful to Aubrey McKibben for this fascinating article. I have been aware of the existence of the Lisnargarvey transmitter for many years but this is a wealth of new interesting information.
Lisnagarvey shared a wavelength (261 m) with Stagshaw in North East England until the mid-sixties. Then Lisnagarvey was given a separate wavelength (224 m), improving the effective range of both transmitters and enabling full regional separation.
I have my own contribution on medium wave transmitters to present after a short break; watch this space.
I can add a few to the Ancient Mariner's helpful initial list.
1214 kHz (247 m) used alongside the Light Programme's long wave transmissions. It came from a few low-to-medium-power transmitters scattered around the country. When the Light was split into Radios 1 and 2, this frequency was allocated exclusively to Radio 1, with a few extra low-power transmitters added. This single-wavelength coverage was less than satisfactory for a radio service which, in those days, did not even have VHF availability.
647 kHz (464 m) used by Radio 3. There was a high-power transmitter at Daventry using this frequency, supplemented by low-power transmitters serving populous areas (e.g. Tyneside) beyond signals of reasonable strength from here.
1546 kHz (194 m) also used by Radio 3, served by a number of low-powered transmitters scattered around the country in populous areas.
Another English speaking service from overseas was the Irish National radio service on 566 kHz (530 m) from the transmitter at Athlone, latterly Tullamore. This service has now been replaced by the long wave transmissions on 252 kHz (1190 m) - the former Atlantic transmitter. Sparkingchip's web link gives a lot of interesting reading about this.
In the summer of 1972 there was a reshuffle of transmitter frequencies, resulting in the following.
Medium wave became available to local radio stations, hitherto using VHF only.
The English Radio 4 regional stations were rationalised into fewer frequencies and many familiar wavelengths changed.
The midland region lost its 1088 kHz (276 m) frequency from Droitwich. This frequency was reallocated to Crowborough for BBC Overseas services. Droitwich switched to another frequency, 1052 kHz (285m), taken over from Start Point in the West. And so the chain continued.
These changes did not affect regional radio Wales, Scotland or Northern Ireland, which still use these frequencies to this day (give or take a kilohertz; see next paragraph).
In November 1978 further changes took place. Frequencies across Europe and Asia were standardised to be exactly divisible by nine. To achieve this, most British medium wave transmitters had their frequency increased by 1 kHz. Some other changes took place at this time.
Radio 4 moved to long wave, 200 kHz (1500 m).
The 1215 kHz (247 m) network was switched from Radio 1 to Radio 3.
BBC overseas from Crowborough changed to 648 kHz (463 m), the frequency formerly used by the now-redundant Daventry Radio 3 transmitter.
Radio 2 now had two main medium wave frequencies, as did Radio 1, substantially improving reception, though it still did not have VHF.
These changes did not take place simultaneously but over several hours stretching from a mid-evening in November overnight. Naturally curious as I am, I had a fun evening, into the night, listening across the medium wave band to what was going on. BBC Overseas, a 24/7 service, was the first to change, with more to do than most. As continental stations progressively changed frequency, there were 1 kHz whistles across many parts of the waveband, caused by beating between interfering transmitters broadcasting 1 kHz apart. By the following morning, all had settled down to the new arrangement.
I still have a useful guide, issued free with the Radio Times at that time. It takes the form of a card with a sliding middle section. I have set it to show the situation for Radio 2, for which the new frequencies are 909 kHz (330 m) and 693 kHz (433 m). Radio 1 was allocated 275 and 285 m.
I've done a bit more digging and found this very interesting and detailed account of the history of medium- and long-wave stations in the UK from birth to the present day (almost).
