The C band is a name given to certain portions of the electromagnetic spectrum, including wavelengths of microwaves that are used for long-distance radio telecommunications. The IEEE C-band (4 GHz to 8 GHz) - and its slight variations - contains frequency ranges that are used for many satellite communications transmissions, some Wi-Fi devices, some cordless telephones, and some weather radar systems. For satellite communications, the microwave frequencies of the C-band perform better under adverse weather conditions in comparison with Ku band (11.2 GHz to 14.5 GHz) microwave frequencies, which are used by other communication satellites. The adverse weather conditions, collectively referred to as rain fade, all have to do with moisture in the air, including rain and snow.
The NATO C-band is the range of radio frequencies from 500 megahertz (MHz) to 1000 MHz in the system of letter designations for frequency bands used by the NATO for electronic countermeasure (ECM) applications. This is equivalent to wavelengths between 0.6 m and 0.3 m. It is a subset of the UHF band as defined by the ITU and the IEEE. This terminology is rarely used by the NATO members that are located in North America.
The IEEE C-band is a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 4.0 to 8.0 gigahertz (GHz); however, this definition is the one followed by radar manufacturers and users, not necessarily by microwave radio telecommunications users.
The communications C-band was the first frequency band that was allocated for commercial telecommunications via satellites. The same frequencies were already in use for terrestrial microwave radio relay chains. Nearly all C-band communication satellites use the band of frequencies from 3.7 to 4.2 GHz for their downlinks, and the band of frequencies from 5.925 GHz to 6.425 GHz for their uplinks. Note that by using the band from 3.7 to 4.0 GHz, this C-band overlaps somewhat into the IEEE S-band for radars.
The C-band communication satellites typically have 24 radio transponders spaced 20 MHz apart, but with the adjacent transponders on opposite polarizations.  Hence, the transponders on the same polarization are always 40 MHz apart. Of this 40 MHz, each transponder utilizes about 36 MHz. (The unused 4.0 MHz between the pairs of transponders acts as "guard bands" for the likely case of imperfections in the microwave electronics.)
The C-band is primarily used for open satellite communications, whether for full-time satellite TV networks or raw satellite feeds, although subscription programming also exists. This use contrasts with direct broadcast satellite, which is a completely closed system used to deliver subscription programming to small satellite dishes that are connected with proprietary receiving equipment.
The satellite communications portion of the C-band is highly associated with television receive-only satellite reception systems, commonly called "big dish" systems, since small receiving antennas are not optimal for C-band systems. Typical antenna sizes on C-band capable systems ranges from 7.5 to 12 feet (2.5 to 3.5 meters) on consumer satellite dishes, although larger ones also can be used.
The C-band frequencies of 5.4 GHz band [5.15 to 5.35 GHz, or 5.47 to 5.725 GHz, or 5.725 to 5.875 GHz, depending on the region of the world] is used for IEEE 802.11a Wi-Fi and cordless telephone applications, leading to occasional interference with some weather radars that are also allocated to the C-band.
Slight variations in the assignments of C-band frequencies have been approved for use in various parts of the world, depending on their locations in the three International Telecommunications Union radio regions. Note that one region includes all of the Americas; a second includes all of Europe and Africa, plus all of Russia, and the third region includes all of Asia outside of Russia, plus Australia and New Zealand. This latter region is the most populous one, since it includes the People's Republic of China, India, Pakistan, Japan, and Southeast Asia.
|C-Band Variations Around The World|
|INSAT / Super-Extended C-Band||6.725–7.025||4.500–4.800|
The Radio Regulations of the International Telecommunication Union allow amateur radio operations in the frequency range 5.650 to 5.925 GHz, and amateur satellite operations are allowed in the ranges 5.830 to 5.850 GHz for down-links and 5.650 to 5.670 GHz for up-links. This is known as the 5-centimeter band by amateurs and the C-band by AMSAT.
Fiber optic communications
- What is C Band page from tech-faq (accessed Aug. 14, 2008)
- Leonid A. Belov; Sergey M. Smolskiy; Victor N. Kochemasov (2012). Handbook of RF, Microwave, and Millimeter-Wave Components. Artech House. pp. 27–28. ISBN 978-1-60807-209-5.
- Norman Friedman (2006). The Naval Institute Guide to World Naval Weapon Systems. Naval Institute Press. pp. xiii–xiv. ISBN 978-1-55750-262-9.
- "V.431: Nomenclature of the frequency and wavelength bands used in telecommunications". ITU-R. 2006-01-04. Retrieved 2014-02-03.
- "521-2002 - IEEE Standard Letter Designations for Radar-Frequency Bands". IEEE. 2003-01-14. doi:10.1109/IEEESTD.2003.94224. Retrieved 2014-02-03. (subscription required (. ))
- Peebles, Peyton Z. Jr, (1998), Radar Principles, John Wiley and Sons, Inc., p 20
- Optical Fiber Communications article in rp-photonics' Encyclopedia of Laser Physics and Technology (accessed Nov. 11 2010)
- The VSAT Installation Manual Video Presentation shows examples of the arrangement of the Feed for c-band polarization requirements
- VSAT Installation Manual with explanation of c-band polarization requirements for a VSAT