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former aviation reflector at black hill Lam Tin



You can see some strange big white rectangular hoardings when you are hiking along wilson trail 3, one is facing north east and the other south west.

The boards were often tagged as 'former aviation reflector'

Many said that it is for aircrafts, during foggy weather, when visibility is low. Common belief is that  they bounce back radio waves. Some say it is microwave antenna

However, when you think more carefully, the shape of it do not reflect the waves back to aircraft as they should, it is rather a wave spreader than a reflector. What is it?

If it is a reflector , it should look like a corner of a square box, or called as corner reflector.


 

It seems to be erected for the Hong Kong airport, likely be the previous Kai Tak airport.

It could be part of the transponder system for air traffic control

transponder

or as special purpose secondary surveillance radar (SSR), or part of the SSR system. The electronics may have been removed after the Kai Tak airport was closed and /or such technology has become obsolete.


 


This site is roughly 1 Nautical Mile from runway

It can also be one of those german freya or  Mammut antenna array radar, working at 120-150 MHz. the main purpose is for identification friend or foe (IFF), or for monitoring large group of birds flying near the airport.

This is most reasonable answer, from Taiwan. Microwave reflection antenna:

These are microwave reflector antennas, an aide to communications transmission. Wireless communications frequently use microwave transmission, but microwaves can be blocked by mountains or other obstacles, so antennas are built on the top of high mountains so that they can relay signals from one side of the mountain to the other. 


 


They are also know as passive microwave repeaters

for the north facing reflector, the reflected beam is ~ N 23-25 deg W, pointing above horizon(up)

for the south facing reflector, the reflected beam is ~S 46-48 deg E, pointing below horizon(down)

 

From a blogger: 

五桂山頂的金屬板是反射微波的。在將軍澳的TVB將電視訊號轉成微波頻道(typ 2-4 GHz)，射向五桂山頂的金屬板，再反射到慈雲山頂(飛鵝山頂?)的數碼地面電視發射站，經訊號轉換(down conversion)DTMB UHF頻道(400-800MHz)廣播。

DH: Decision Height

DME:  Distance Measuring Equipment

DVOR: Doppler VHF Omindirectional Radar range

MM: middle marker
NDB RW: NDB Runway

NDB: C

OM : outer marker

RDL: Radial

SL: Speed Limit

TH: Threshold

Civil Aviation Department

Primary and Secondary Surveillance Radar system in Hong Kong

go2nature

flynwill 

gigawave

passive repeater wiki 

rfcafe

台灣天面山 山頂反射電波板

ICAO abbreviations

Stephenchan blog

on google map


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