Marking the end of Radio 4 Long Wave from Droitwich in September 2026

I am not the right person to answer the main questions you pose, but your maps show why at least pre-internet long waves were the way to get coverage at the scale of whole countries, and how the radio tele-switching was possible. Your Berlin listening tests are also of interest, as they do show that the whole of the path (including the bit that is up in the air ) all needs to have been in darkness for some time for the decay of the ionization to take effect. The ion lifetimes (recombination times) in the different layers are very variable - where there is almost no atmosphere the random walk before suitable event is very long. 
I suspect your sensitivity would have been external noise limited in a city location, rather than the natural noise floor, but it is hard to tell, and as interference can equally come in from hundreds of miles away, predition of that is very hard.

I agree with your sentiment, that it would be great shame is this end of an era was not marked in some way - there was so much remarkable pioneering development that went into getting long wave (well radio generally) to work in the first place, and the knowledge is dying off as those who did it are leaving us. It is unfortunate that LW and MW are almost of no value for listening now as there is so much buzzing and feezling from random electronics that an indoor portable radio is nowadays  almost useless in many households.
Mike

As far as I am aware, the current intention is to shut-down medium wave (MW) broadcasting in the UK by 2027 and I would imagine the same timeframe may apply to long wave (LW) broadcasting too.

Searching online, I found the following link (in German) that gives the very specific date of 26 September 2026 for the shut-down of BBC Radio 4 LW on 198 kHz, which would be consistent with the the intention for a complete shut-down by 2027.

https://www.radioeins.de/programm/sendungen/medienmagazin/radio_news/beitraege/2021/bbc_langwelle.html

That said, I have lost count of how many dates for the shut-down of BBC Radio 4 LW have came and went over the past few years! 

The article mentions the Lisnagarvey Transmitting Station in Northern Ireland, which now has only two out of its original five MW stations remaining on air, showing the MW shut-down is well underway.

When BBC Radio Ulster on 1341 kHz from Lisnagarvey was shut-down in 2021, I don't think there was anything special to mark the occaision - as far as I know, the programming stopped and was replaced with a recorded annoucement for a few weeks, before the transmitter was finally switched off.

- Ross

Official UK Government guide recommends preparing an emergency kit at home, in case of a national emergency.

The kit list includes:

• Battery or wind-up radio to get updates during a power cut – a car radio can be used, however in severe weather it might be safer to stay inside. 
  
  
  prepare.campaign.gov.uk/.../

Hugh Breidenbach said:

Nostalgia aside, BBC Radio 4 Long Wave has served UK business, culture, and defence, from maritime broadcasts to national contingency communication.  A programme to duly commemorate the closedown ought to be in the pipeline.  A number of people would like to contribute to it.

In that list of services needs to be included 'Radio Teleswitch' which was a form of early radio controlled smart metering system, it supported time of use tariffs and was able to automatically control loads like storage heaters, switching them to run during off-peak periods which could be adjusted dynamically to manage the load on the distribution networks, system as a whole and according to weather conditions.

What is most impressive is this was being done 40 years ago in the 1980s, and here we are 40 years later and we're still struggling to put in place similar capabilities for dynamic control of new loads like EV charging and heat-pumps, yet it was being done with a fraction of the technology decades ago!