David Looser wrote:

"Don Pearce" wrote

Flash memory is good, but not terribly useful for keeping a clock
ticking.

True, but for keeping tuning presets flash seems to be the obvious choice.
Why so many radios use volatile RAM for this is a mystery to me.

You really do need a battery or capacitor. If this part of
the circuit is made from something like CMOS, then it should be
possible to hang on to the time for days.

A "ticking" clock will consume far more current than simply storing data. A
capacitor won't do for that, it does require a battery.

But frankly, in the UK this is all a bit moot. Power failures are
rare, and they don't last very long when they happen. I have a few
clock radios that should have batteries. Over the years the batteries
have all run down and I haven't bothered replacing them, very
occasional clock resetting is far less bother.

I agree 100% with that. My experience is that clock-radios run their
batteries down quite quickly once the mains is disconnected, and those
batteries are expensive to replace. I don't bother to replace them either.

And if you fit a rechargeable battery it's usually run down through
self-discharge by the time it's needed !

Graham