cavity filter การใช้

The filter may be made from cellulose acetate fibre, paper or activated charcoal ( either as a cavity filter or embedded into the cellulose acetate ).
Still widely used in the 40 MHz to 960 MHz frequency range, well constructed cavity filters are capable of high selectivity even under power loads of at least a megawatt.
In the microwave range ( 1000 MHz ( or 1 GHz ) and higher ), cavity filters become more practical in terms of size and a significantly higher quality factor than lumped element resonators and filters.
Physical length of conventional cavity filters can vary from over 205 cm ( 82 " ) in the 40 MHz range, down to under 27.5 cm ( 11 " ) in the 900 MHz range.
When a transmitter needs to be colocated with a receiver where the frequency difference is very small ( " for example 145.000 and 145.600 MHz " ) the cavity filters can be used on both the transmitter and the receiver to improve the purity of the transmitter and the immunity of the receiver.