Where the cell phone and cell phone blocker are sold

Waves reach the surface of the shield reflection energy generated mainly due to media (air) is inconsistent with the metal caused by the wave impedance, the greater the difference between the two, the greater the loss caused by the reflection; and reflection and frequency, the lower the frequency, more serious reflection. When penetrating the shield electromagnetic waves in the energy absorption loss was mainly due to eddy currents induced. Vortex on the one hand have the opposite magnetic field to offset the original magnetic field interference, and thermal losses. Therefore, the higher the frequency, the thicker the shield, eddy current loss is also greater. 2.2.3 shielding effectiveness is defined and calculated by the cabinet of the shielding effect of the electromagnetic field strength of the cabinet to assess the degree of weakening, usually shielding effectiveness as a yardstick.No matter where the cell phone and  cell phone blocker are sold, the quality and after-service should be guaranteed for clients.  Shielding effectiveness is defined as the test point is not in the same time shielding the field strength increases with the field strength increases after masking ratio. SE said that with the shielding effectiveness in dB units.
Schematic diagram of the shielding effectiveness of shielding effectiveness expression: P point when the electric field strength unshielded; ES as shown in Figure (b), with a little added masked the electric field strength. It can also use the ratio of magnetic field strength is defined. HO is a point where no shielding magnetic field strength; HS additional shielding for the same point after the magnetic field strength. The shielding effectiveness of the theoretical value determined by three factors, namely, A (absorption loss), R (return loss), K (multiple reflection coefficient).Of course, the price of cell phone and  cell phone jammer  is also the concern of the client.  Its expression is: 1. Absorption loss into energy in penetrating the shield when the shield has the energy of the decay, when the electromagnetic wave propagation in shielding the body, due to attenuation resulting from absorption, as absorption loss. It has nothing to do with the type of wave, and the shield thickness, frequency, conductivity and permeability related. Absorption loss A (dB) of the expression: where, d is the thickness of shielding material (mm); f is the frequency of electromagnetic wave shielding body phase; of permeability; σ r is the shield of the relative conductivity of copper 2 Return loss due to air and metal shield electromagnetic impedance is different, the incident electromagnetic wave will have the role of reflection. The manufacturer should pay much attention to the quality of cell phone and  cell phone jammer . But in a different field sources and field area, the electromagnetic impedance of air is not the same. Return loss in a magnetic field R (dB) is calculated as: formula for the relative permeability; σ r is the relative copper shield conductivity, σ r = wave frequency (Hz) for the radiation to shield The distance between (mm). ; D near field source of the electric field reflection loss R (dB) as follows: the surface reflection loss that shield the reflection of the incident, is to shield electromagnetic waves incident from space, in the interface due to reflection, so that the attenuation of electromagnetic energy . When the incident electromagnetic wave shielding layer to the surface when the surface appeared in the reflected wave and transmitted wave two kinds of waves.  cell phone jammer has the various sales channels and selling modes.As the transmitted wave attenuation within the shield, the shield and hit the other side of the surface, so they were on this side of the reflection and transmission, reflected again by internal waves, and so forth cycle for reflection, so the energy quickly attenuation.