Theomach

There is a delightful novel by Larry Niven called Ringworld. The idea behind the book is a band of people search a ring where the internal side is built like a planet (Think the ring in the game Halo, but 1 million miles in diameter). When they begin to search the ring it takes a while before they meet the inhabitants, but eventually they come across some.

Basically what had happened is the civilisation that had been created on the ring fell when they ran out of power to control the hovering buildings and all the cities were turned to rubble as they fell, and the people resorted to barbarians living in the ruins.
The ring itself was made of metal with about 40 feet of land above it (If the numbers are wrong forgive me the point is still the same). This stopped the people from bringing civilisation back because there were no elements for them to harvest, and technology could not evolve like it had on Earth initially.
However, they did come across some floating buildings, i.e. those that had their own power, and some buildings with defence mechanisms still functioning.

The point I am trying to make is, technology will only survive as long as there is energy to power it, and when we run out of power, technology will have to evolve again.

I know this is based on a fictional book, and we have the fortune of still having things that didn't rely on power to fall back on, but you can see where I'm coming from.

And as for your question about the radio, she an only listen to it if there is still someone broadcasting something, regardless of if the radio itself is working. Chances are you'd just get some government warning over and over again.
Or Abba repeats.