Not generally known, but Radio 4 on LW is a highly stable frequency reference and also [0] carries a digital time signal (along with other broadcast data, like signals for electricity meters). It's done by phase-modulating the carrier and is pretty easy to extract using analogue techniques or simple SDR (e.g. downmix to audio and extract the phase using a soundcard).
Having said all that, looks like it's being turned off next year [1]. Let's hope someone tells the sub commanders!
[0] I presume it still does, been a while since I checked.
Having said all that, looks like it's being turned off next year [1]. Let's hope someone tells the sub commanders!
[0] I presume it still does, been a while since I checked.
[1] https://www.bbc.co.uk/mediacentre/articles/2023/bbc-radio-4-...