Here is the non-computer based system I have been using for years,
mainly to record talk radio:

Used Sharp mini-disc recorder
Radio with a mechanical on-off switch
Digital timer (such as Intermatic 17C)

set radio to desired frequency, leave it in "on" position
set digital timer to desired on/off times
plug radio AC cord into the digital timer
connect digital timer to AC outlet
connect radio to mini-disc recorder (patch cord from radio line-out or
headphone jack to mini-disc line-in)

connect Sharp mini-disc recorder to an AC outlet
set Sharp mini-disc to record /synch on.

The digital timer will power the radio on/off based on your timer
settings.
When the audio signal gets to the Sharp mini-disc recorder, it will
begin recording. When there is no longer a signal (timer shuts radio
off), the recording stops and the mini-disc recorder goes back to
synch-mode awaiting the next audio from the radio.

Do not have the digital timer control the mini-disc (you want that in
on/synch mode all the time).

Only Sharp mini-disc recorders will work for this, Sony's do not.
Sharp's synch-record analog signals while Sony's do not do that.

You will have to find a used Sharp mini-disc recorder as they are no
longer offered. They come up on ebay from time to time. Suggest you
get a later model MDLP recorder, as it will allow you to record more
stuff on a disc.

A really neat system. So much better than cassettes. I prefer a
stand-alone, non computer reliant set up.

This works if you are only recording the same radio frequency - which
is all I do. If I was going to do multiple frequencies, I'd need to
dedicate another radio/timer combo to the other frequency and connect
them all to the mini-disc input with an adapter that has multiple
jacks in.

If you are only recording brief periods, you can dispense with the
timer. Use radios that have on/off timers.

I record 4 sessions a day (three 1 hour segments, one 2 hour
segment). I have never found a radio that will handle that from a
timer perspective. Some radios will allow you to have three timer
sessions (up to one hour each) on different frequencies.