# What's the upside of L, S and C bands for military search radars? **URL:** \ **Category:** Factual Questions\ **Created:** [June 7, 2015, 1:36am UTC](https://boards.straightdope.com/t/whats-the-upside-of-l-s-and-c-bands-for-military-search-radars/721853 "2015-06-07T01:36:58Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![MichaelEmouse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/michaelemouse/32/101_2.png) [@MichaelEmouse](https://boards.straightdope.com/u/MichaelEmouse)\ **Post date:** [June 7, 2015, 1:36am UTC](https://boards.straightdope.com/t/whats-the-upside-of-l-s-and-c-bands-for-military-search-radars/721853/1 "2015-06-07T01:36:58Z")
I understand why tracking radars would use X-band and higher the importance of resolution for tracking. For a given antenna size, though, a higher frequency also means that the antenna gain is greater which means more range. Most airborne platforms only have enough room for a small antenna so they use X-band for search, tracking and target illumination. They typically increase the time-on-target, frequency and PRF when they switch to tracking and increase frequency while using continuous wave for target illumination. Most platforms large enough to carry a larger antenna use L, S or C band for search. For example: Land-based platforms: > **[2K22 Tunguska](https://en.wikipedia.org/wiki/2K22_Tunguska)** > > The 2K22 Tunguska (Russian: 2К22 "Тунгуска") is a Soviet tracked self-propelled anti-aircraft weapon armed with a surface-to-air gun and missile system. It is designed to provide day and night protection for infantry and tank regiments against low-flying aircraft, helicopters, and cruise missiles in all weather conditions. The NATO reporting name for the missile used by the weapon system is SA-19 "Grison". > Development of the 2K22 anti-aircraft system began on 8 June 1970. At the request of the S... “An electromechanically scanned parabolic E-band (10kW power) target acquisition radar is mounted on the rear top of the turret that when combined with the turret front mounted J-band (150kW power) monopulse tracking radar forms the 1RL144 (NATO:Hot Shot) radar system” > **[ZSU-23-4 Shilka](https://en.wikipedia.org/wiki/ZSU-23-4)** > > The ZSU-23-4 "Shilka" is a lightly armored Soviet self-propelled, radar-guided anti-aircraft weapon system (SPAAG). > The acronym "ZSU" stands for Zenitnaya Samokhodnaya Ustanovka (Russian: Зенитная Самоходная Установка), meaning "anti-aircraft self-propelled system"; the "23" signifies the bore diametre in millimetres; the "4" signifies the number of gun barrels. It is named after the Shilka River in Russia. Afghan soldiers nicknamed it the "sewing machine" due to the sound of its cannons firin... “The upgraded vehicle is equipped with the ASADS Ka-band target tracking radar and the PAGE I-band surveillance radar” Sea-based: The Arleigh Burke class destroyers mainly use the S-band AN/SPY-1 and the C-band AN/SPS-67 for search ( [AN/SPY-1 - Wikipedia](http://en.wikipedia.org/wiki/AN/SPY-1) and [AN/SPS-67 - Wikipedia](http://en.wikipedia.org/wiki/AN/SPS-67)) The Ticonderoga class cruiser uses the L-band AN/SPS-49 ([AN/SPS-49 - Wikipedia](http://en.wikipedia.org/wiki/AN/SPS-49)) So, why do search radars tend to use the L, S and C bands? They could use X band as well and get even more antenna gain with their bigger antenna. From what I’ve seen, the attenuation in X-band isn’t that bad. Have I got that wrong? Is it chiefly a way to defeat the low observability characteristics which are integrated into some fighters and bombers? Is, say, C-band significantly better at detecting low observability planes than X-band? Is it because a larger beamwidth in a search radar is a desirable characteristic since it allows faster (if less precise) scanning of a given area? I’ve read that a lower frequency will produce a stronger signal for a given power input. Is this true? If so, I have a difficult time figuring out the tradeoffs between the stronger signal of the lower frequency and the greater antenna gain of the higher frequency. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [June 7, 2015, 2:33am UTC](https://boards.straightdope.com/t/whats-the-upside-of-l-s-and-c-bands-for-military-search-radars/721853/2 "2015-06-07T02:33:29Z")
L S and C bands aren’t attenuated as much by water vapor which makes them better suited for long range search radar. X band attenuates more through the atmosphere, but is good enough for airborne radar. You are correct that the choice of using X band for airborne radar is based largely on the antenna size. X band is attenuated more, but it’s good enough for short to medium range airborne use. ---
**Author:** ![MichaelEmouse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/michaelemouse/32/101_2.png) [@MichaelEmouse](https://boards.straightdope.com/u/MichaelEmouse)\ **Post date:** [June 7, 2015, 5:46pm UTC](https://boards.straightdope.com/t/whats-the-upside-of-l-s-and-c-bands-for-military-search-radars/721853/3 "2015-06-07T17:46:40Z")
> [@engineer\_comp\_geek](#): > > X band is attenuated more, but it’s good enough for short to medium range airborne use. I guess atmospheric attenuation becomes less of an issue as you go up in altitude also. A plane at altitude would only have to deal with sparse atmosphere when detecting another plane. When detecting a ship, the ship’s greater RCS would probably help the plane more than the ship’s lower frequency would help the ship.