To reduce the constant losses

To reduce electric interference

To increase the quality of sound

To increase the efficiency of receivers

Minimizes copper use

Reduces hysteresis loss

Reduces eddy current loss

Reduces the space for core

Silica gel

Sodium chloride

Ammonium chloride

Charcoal and salt mixture

More losses

Heavier in weight

Poor voltage regulation

Cannot isolate the secondary winding

Air natural

Oil natural air blast

Oil forced air forced

Oil natural air natural