What happened in the 17th and 18th centuries when solar output decreased just a little bit (indicated by almost no sunspots)?

Little Ice Age Period...

Explanation:

In 17th and 18th century, there was a little period of ice age in Europe and North America. However, there was no sun spots noted in  the sun that are called as solar minima yet there was a little ice age period that some refer to arise of global cooling.

Astronomers and other scientists are also working on the study of sun like stars and Earth like planets that'll eventually helps us to predict the next ice age if it is ever going to be happened.

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia