Deflection Yoke Coil(DY) is a device which is used for the deflection of the electron beams in cathode-ray tube. It is consist of two coils, the horizontal deflection coil and the vertical deflection coil, where a ferrite core is used inside the vertical deflection coil.
In order to reduce the outside magnetic fields produced by these horizontal and vertical DY coil, approximate method of calculating the outside field by the multipole expansion after dipole and quadrupole moments in free space is used. The effect of the ferrite is roughly accounted by the image method.
Outside magnetic fields produced by 24 inch television are measured. Quantitative analysis based upon the quadrupole moments from the front band coils leads to the bending of these coil which makes the outside fields reduced. It is shown by the measurement that the magnetic field of 107[nT] about 50[cm] apart from the TV screen is reduced to 17[nT] by this bending. It is much better than the use of the cancelling coil in use today.