Dielectric plates are used to convert circularly polarised signals to linear polarisation. They work by utilising the difference in dielectric constant between fibreglass (or teflon) and air.
Signals entering a waveguide parallel to the plate will undergo a phase shift different to the signal entering the waveguide at 90 degrees to the plate.
This dielectric plate is typically inserted into a C band LNBF and will typically result in 3dB of signal degradation, which equates to the loss of half of your reflector size. For example if you are receiving a signal with a 3m dish and insert a dielectric plate from receiving a circularly polarised signal the dish will only be able to perform the equivalent of a 1.5m dish.
An alternative method of converting linear satellite signal is to use a waveguide polariser, which doesn’t experience the loss associated with a dielectric plate. A waveguide polariser is a cylindrical device which is stepped to convert the signal from linear to circular. Our F1342 Av-Comm C band polariser is very popular with European and American customers because of its efficiency.