Syllabus Sections:-

Screening

Not in the Full 2021 syllabus Recall that screening with thin metal sheet is effective in reducing unwanted radiation from equipment and/or between stages within equipment.

It is often necessary to keep RF away from parts of a circuit or to prevent coupling of one part of the circuit with another. This is often the case when dealing with tuned circuits. The part of the circuit that needs protection is placed in a thin metal enclosure which is connected to the earth of the circuit.

When used with tuned circuits the "screening can", as the enclosure is sometime called, must be more than 1 1/2 times the diameter of the coil otherwise the Q of the coil will be degraded.

Also a screen may be needed to prevent a strong signal feeding back from one part of the circuit to an earlier stage.

Aluminium, copper or tin are suitable materials at RF.