A passive repeater or passive radio link deflection, is a reflective or sometimes refractive panel or other object that assists in closing a radio or microwave link, in places where an obstacle in the signal path blocks any direct, line of sight communication. Compared to a

microwave radio relay Microwave transmission is the Data transmission, transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300 MHz to 300 GHz (1 m - 1 mm wavelength) of the electromagnetic spectrum ...

station with active components, a passive repeater is far simpler and needs little maintenance and no on-site electric power. It also does not require additional frequencies, unlike active

repeater In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. 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 ...

stations which use different transmit and receive frequencies to prevent crosstalk. The corresponding disadvantage is that without amplification the returned signal is significantly weaker, although in some configurations they can actually provide gain of 100 to 130 dB for UHF and microwave radio-relay stations. Passive radio relay link deflection systems in the vertical level can be realized by receiving the signal with a

parabolic antenna A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or p ...

and leading it through a waveguide to a second parabolic antenna, where it is radiated. For passive

link deflections in the horizontal plane, flat surfaces of metallic material are used, arranged so that the angle of incoming beam corresponds to the angle of the outcoming signal. The resulting structure resembles a

billboard A billboard (also called a hoarding in the UK and many other parts of the world) is a large outdoor advertising structure (a billing board), typically found in high-traffic areas such as alongside busy roads. Billboards present large advertis ...

. Similar systems are used also occasionally for TV relay transmitters or as tunnel transmitters. In these cases, a Yagi antenna receives the transmitted signal and supplies it by way of a

coaxial cable Coaxial cable, or coax (pronounced ), is a type of electrical cable consisting of an inner Electrical conductor, conductor surrounded by a concentric conducting Electromagnetic shielding, shield, with the two separated by a dielectric (Insulat ...

to a second Yagi antenna.

Photos of passive microwave repeaters

See also external links for photos of variety of other passive repeaters. File:Microwave_repeaters_Black_Hill_Hong_Kong.png, Passive Microwave repeaters on Black Hill, Hong Kong File:Black Hill Hong Kong microwave repeater.jpg, Closer view of one of the Passive Microwave repeaters on Black Hill, Hong Kong File:無給電中継装置.jpg, Passive Microwave repeater on a hill in Nagano, Japan

External links

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Passive Repeater Engineering, Microflect, Co. Inc, 1989
*

References

{{Reflist Telecommunications infrastructure it: Ripetitore