Editing Radio telescope (section)

===Frequencies===
The increasing use of radio frequencies for communication makes astronomical observations more and more difficult (see [[open spectrum#Radio astronomy needs|Open spectrum]]).
Negotiations to defend the [[frequency allocation]] for parts of the spectrum most useful for observing the universe are coordinated in the Scientific Committee on Frequency Allocations for Radio Astronomy and Space Science.
[[File:Atmospheric electromagnetic opacity.svg|thumb|upright=1.8|Plot of Earth's atmospheric [[transmittance]] (or opacity) to various wavelengths of [[electromagnetic radiation]].]]
Some of the more notable frequency bands used by radio telescopes include:
* Every frequency in the [[United States National Radio Quiet Zone]]
* [[Channel 37]]: 608 to 614&nbsp;MHz
* The "[[Hydrogen line]]", also known as the "21 centimeter line": 1,420.40575177&nbsp;MHz, used by many radio telescopes including [[The Big Ear]] in its discovery of the [[Wow! signal]]
* 1,406&nbsp;MHz and 430&nbsp;MHz <ref>{{cite web|url=http://www.jb.man.ac.uk/~pulsar/Education/Tutorial/tut/node115.html |title=Microstructure |website=Jb.man.ac.uk |date=1996-02-05 |access-date=2016-02-24}}</ref>
* The [[Waterhole (radio)|Waterhole]]: 1,420 to 1,666&nbsp;MHz
* The [[Arecibo Observatory]] had several receivers that together covered the whole 1–10&nbsp;GHz range.
* The [[Wilkinson Microwave Anisotropy Probe]] mapped the [[cosmic microwave background radiation]] in 5 different frequency bands, centered on 23&nbsp;GHz, 33&nbsp;GHz, 41&nbsp;GHz, 61&nbsp;GHz, and 94&nbsp;GHz.