Ferrite Rod, 100mm long, 3/8 inch Diameter





Ferrite is a ceramic material with a high iron atom content.  It has high magnetic permeability, but low electrical conductivity compared to iron metal.  The low conductivity helps to reduce radio frequency eddy currents in the material, which would reduce the Q factor.  That would make the set very insensitive and the tuning extremely broad.  In the schematic symbol the pins labelled 3 and 4 are the large main tuning coil and the pins labelled 5 and 6 are the smaller output coupling coil shown at the top in the picture.  Pins 1 and 2 and the associated winding are not present on our coil.  In a different design, an extra winding like that could be used at the bottom end of the rod to connect to an external aerial and earth.  That would be needed if you wanted to remove the ferrite rod in order to tune the shortwave broadcast bands.  I've covered SW reception here: Breadboard Transistor Radio Modifications

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