You only need a half-decent microphone.
You could do it on a bad microphone if you wanted!
The Archers is a timeless part of the background noise in many family kitchens in the UK. Seems a shame not to fight through this little piece of calm for normal families in this time of crisis.
If BBC4 goes down, but you're still able to call London on a satellite phone, you don't go nuking Russia. If you have a half dozen different signs of nuclear war and BBC4 is down, it's a point in the "well shit" direction.
So if Northwood goes silent, but the cricket is uninterupted, there's probably something wrong with Northwood. If everything's gone, there's probably something wrong with your radio. But if Northwood's gone, the BBC's gone, but VOA is still up .. you start wondering if something's wrong with the UK.
(For example. I'm not privy to anything the rest of us aren't. But it's clear that it's an item on a checklist that happens to have some novelty value, rather than being our "systema perimetr".)