View source for HR-280

[[File:Type_366_radar.jpg|300px|thumb|right|A HR-280ND radome atop the bridge of the frigate Chŏnsŏng, taken around the year 2000]]
The '''HR-280''' ([[Menghean language|Menghean]]: 해군 레이다 280, ''Haegun Reida 280'') is a long-range surface-search radar system in service with the [[Menghean Navy]]. It is frequently seen on medium to large-size warships, such as destroyers, frigates, and some corvettes, usually mounted on top of the bridge. The manufacturer's website claims that it can detect surface targets at ranges of up to 250 kilometers in active mode and 400 kilometers in passive mode.

==Description==
The HR-280 is a highly capable surface-search radar designed to exploit {{wp|Atmospheric_duct|atmospheric ducting}} and {{wp|Inversion_(meteorology)|temperature inversion}} to produce {{wp|Creeping_wave|creeping waves}} in radio frequencies not normally subject to strong atmospheric diffraction or reflection. This allows a warship carrying the system to detect enemy destroyer-sized targets at ranges of over one hundred kilometers, even when the nominal {{wp|Radar_horizon|radar horizon}} is only 20 to 30 kilometers away.

Notably, while the HR-280 is capable of detecting surface warships beyond the horizon, it is not a "true" {{wp|Over-the-horizon_radar|OTH radar}} system. Its lowest active frequency is in the {{wp|J_band_(NATO)|J-band range}}, while true OTH-B and OTH-SW systems operate in the 3-30 MHz range. Consequently, HR-280 can be contained within a much smaller radome than true OTH systems, which require land-based arrays more than a kilometer in length.

The disadvantage of the HR-280's approach, however, is that it remains highly dependent on climate conditions, such as the presence of {{wp|Atmospheric_duct|atmospheric ducts}}, to diffract electromagnetic signals in its operating bands. Thus, while the active detection mode can pick up surface contacts at ranges of up to 250 kilometers under ideal atmospheric conditions, the detection range can fall to regular radar-horizon levels when these conditions have passed, with extensive fluctuation in between. In the warm, humid waters of the South Menghe Sea, temperature inversions and the diffraction conditions they bring may occur 20-30% of the time on average; near land, as around the Strait of Portcullia, that ratio rises to 40-60%. Some sources speculate that the Menghean Navy may plan its offensive operations around such favorable conditions, attacking during overcast weather or immediately after sundown, while others maintain that the Menghean Navy has shifted toward a more flexible approach.

Even under optimal conditions, the HR-280's signal resolution is poor, due to unpredictable qualities of the atmosphere itself. This effect can also be seen in visual-band distortion, i.e. the {{wp|Fata_Morgana_(mirage)|Fata Morgana}}. As such, it cannot be used to target surface-to-air weapons, and it provides only a rudimentary firing solution for anti-ship missiles. Menghean sources note that it would constitute only one aspect of a wider range of detection measures, such as helicopter-borne radar and land-based maritime patrol aircraft.

==Configuration==
The original HR-280G system consisted of two types of radome: HR-280ND, a large dome containing a radar dish in active mode (emitting and listening), and HR-280SD, a smaller dome containing a radar dish in passive mode (listening only). In this configuration, a warship would usually carry one HR-280ND radome atop the bridge and one HR-280SD radome on either side of the superstructure.

The newer HR-280N system combines both active and passive dishes in a back-to-back configuration within a single radome, reducing the amount of deck space required. It also significantly improves the processing subsystems for both modes.

When fitted with microwave-frequency datalinks, ships carrying the HR-280 system can relay target information to other warships nearby, as long as they have direct line-of-sight contact. Some sources suggest that this could be used to triangulate a target's location more precisely, even if only passive or highly distorted active signals are available.

==Specifications==
* Height (radome): 3.20 meters
* Diameter (radome): 3.35 meters
* Weight: 3800 kg
* Maximum detection range, active: 250 kilometers
* Maximum detection range, passive: 400 kilometers
* Frequency range, active: J-band
* Frequency range, passive: J, G, E/F, D-bands
* Number of targets processed: up to 50

[[Category:Menghe]]