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What does a cavity filter do?
Cavity filters are a type of resonant filter used for either passing desired RF signals within a specified frequency range or rejecting RF signals within a range of frequencies.
When would you use a repeater?
Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Some types of repeaters broadcast an identical signal, but alter its method of transmission, for example, on another frequency or baud rate.
What is inside a duplexer?
What is a duplexer? A duplexer typically consists of two band pass filters connected in parallel. One filter provides a path between the transmitter and the antenna, the other provides a path between the antenna and the receiver. No direct path between the transmitter and receiver exists.
Is cavity a high pass filter?
The resonators and cavities are silver plated for low RF resistivity, in order to achieve low insertion loss and high selectivity. The cavity band pass filters range in length from 1 in. to more than 18 in., depending on number of sections, insertion loss, power handling, and center frequency.
Is duplexer an amplifier?
A duplexer is an electronic device that allows bi-directional (duplex) communication over a single path. In radar and radio communications systems, it isolates the receiver from the transmitter while permitting them to share a common antenna. Most radio repeater systems include a duplexer.
Why do you need a cavity filter for ham radio?
This can be very useful when ham repeaters are situated very close to other spectrum users such as pager whose unwanted signals can interfere with the ham radio equipment. Cavity filters are a very effective way to create a “notch” at the repeater frequencies. Why use a cavity when other tuned circuits can do the job?
What kind of filter does a cavity filter use?
Cavity filters are a type of resonant filter used for either passing desired RF signals within a specified frequency range or rejecting RF signals within a range of frequencies.
Why are there minimum and maximum frequencies for cavity filters?
Because of the x/4 wavelength “rule” there is a practical minimum and maximum frequency at which a particular design can operate due to the size of the cavities, and length of the cables between the cavities: At lower frequencies the cavities will be larger and the interconnecting cables longer
What happens to power handling capacity of cavity filter?
Above 1 dB, the power handling capacity of the cavity is reduced due to internal voltages. Cavity filter effects are additive; to achieve high “Q” values, it is usually best to string two or three cavities together, enabling lower system insertion loss.