When the sunspots are really low, there are still radio things that can be
done. Disassemble the old solar powered calculator you got as a freebie and
use it to power a one transistor oscillator, using one of the many old odd
ball crystals you have in a drawer. Then put in a plastic box an hook a
piece of wire to it and place it outside. When the sun shines, the radio
will transmit. The more you have, the more signals you will hear. You can
place many around the neighborhood, if you are into dx.

Since the crystal will be affected by temperature, you can calibrate the
actual received frequency with outside temperature and impress your friends.

Colin K7FM