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 Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300MHz to 300GHz(1 m - 1 mm wavelength) of the electromagnetic spectrum. Microwave signals are normally lim ...

, in places where an obstacle in the signal path blocks any direct,

line of sight The line of sight, also known as visual axis or sightline (also sight line), is an imaginary line between a viewer/observer/ spectator's eye(s) and a subject of interest, or their relative direction. The subject may be any definable object taken ...

communication. Compared to a microwave radio relay 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. Som ...

stations which use different transmit and receive frequencies to prevent feedback. 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 u.h.f. 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 and leading it through a

waveguide A waveguide is a structure that guides waves, such as electromagnetic waves or sound, with minimal loss of energy by restricting the transmission of energy to one direction. Without the physical constraint of a waveguide, wave intensities de ...

to a second parabolic antenna, where it is radiated. For passive microwave radio relay 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.Radio Mirrors for Communications, May 1969 Electronics World
/ref> Similar systems are used also occasionally for TV relay transmitters or as

tunnel transmitter A tunnel transmitter allows wireless reception in tunnels. It consists of a receiving antenna which receives the signal to be radiated in the tunnel, and a transmitting antenna installed in the tunnel, which is either a Yagi antenna or a line anten ...

s. In these cases, a

Yagi antenna Yagi may refer to: Places * Yagi, Kyoto, in Japan * Yagi (Kashihara), in Nara Prefecture, Japan * Yagi-nishiguchi Station, in Kashihara, Nara, Japan * Kami-Yagi Station, a JR-West Kabe Line station located in 3-chōme, Yagi, Asaminami-ku, Hiroshima ...

receives the transmitted signal and supplies it by way of a coaxial cable to a second Yagi antenna.

Photos of microwave repeaters

See also external links for photos of variety of other passive repeaters. File:Microwave_repeaters_Black_Hill_Hong_Kong.png, Microwave repeaters on

Black Hill, Hong Kong Black Hill () is a hill in Hong Kong with a height of 304 metres. It is located between the communities of Lam Tin, Kowloon and Tiu Keng Leng, Sai Kung. Name It is named for former administrator Major General Wilsone Black, a British Army o ...

File:Black Hill Hong Kong microwave repeater.jpg, Closer view of one of the Microwave repeaters on

File:無給電中継装置.jpg, Microwave repeater on a hill in Nagano, Japan

External links

Radio Mirrors for Communications, May 1969 Electronics World

Passive Repeater Engineering, Microflect, Co. Inc, 1989

References

{{Reflist Telecommunications infrastructure it: Ripetitore