Electromagnetic shielding properties of amorphous alloy shields for cathode ray tubes

Because of the excellent soft magnetic properties of the amorphous alloy Fe40Ni38Mo4B18 (2826MB), we have made funnel‐shaped shields for cathode ray tubes by combining the amorphous ribbons and ferromagnetic powders via resin transfer molding composite technology. The electromagnetic shielding properties of shields were improved by increasing the thickness of ribbons and the weight percentage of ferromagnetic powders. For a shield with six‐layer ribbons, the maximum magnetic shielding effectiveness obtained near the applied magnetic field 2 Oe (dc and ac 60 Hz) was about 25–27 dB, and the magnetic shielding factors were improved to 27–30 dB by adding the ferromagnetic powders. After the field annealing of shields, the magnetic shielding effectiveness increased and the maximum values of 35–40 dB were shifted near the applied magnetic field 0.2 Oe. The electric field shielding effectiveness over the broadband spectrum 10 kHz–18 GHz was in the range 50–80 dB.