Editing Wow! signal (section)

== Signal measurement ==
[[File:Wow signal profile.svg|thumb|Plot of signal intensity versus time]]
The string 6EQUJ5, commonly misinterpreted as a message encoded in the radio signal, represents in fact the signal's [[Intensity (physics)|intensity]] variation over time, expressed in the particular measuring system adopted for the experiment. The signal itself appeared to be an unmodulated [[continuous wave]], although any [[modulation]] with a period of less than 10 seconds or longer than 72 seconds would not have been detectable.<ref name="Calib Wow">{{Cite web |last=Shuch |first=H. Paul |date=November 9, 1996 <!--Presented to the AMSAT Annual Meeting and Space Symposium, Tucson AZ--> |title=SETI Sensitivity: Calibrating on a Wow! Signal |url=http://www.setileague.org/articles/calibwow.htm |access-date=June 25, 2016 |publisher=SETI League}}</ref><ref>{{Cite book |last=Ehman |first=Jerry R. |url=https://books.google.com/books?id=jAk9bTm3Sj4C |title=Searching for Extraterrestrial Intelligence: SETI Past, Present, and Future |publisher=Springer |year=2011 |isbn=978-3-642-13196-7 |editor-last=Shuch |editor-first=H. Paul |page=59}}</ref>

=== Intensity ===
The signal intensity was measured as [[signal-to-noise ratio]], with the noise (or baseline) averaged over the previous few minutes. The signal was [[Sampling (signal processing)|sampled]] for 10 seconds and then processed by the computer, which took 2 seconds. The result for each frequency channel was output on the printout as a single [[alphanumeric]] character, representing the 10-second average intensity, minus the baseline, expressed as a [[dimensionless]] multiple of the signal's [[standard deviation]].<ref name="code">{{Cite web |last=Ehman |first=Jerry |title=Explanation of the Code "6EQUJ5" On the Wow! Computer Printout |url=http://www.bigear.org/6equj5.htm |access-date=July 2, 2016 |publisher=Ohio History Central}}</ref>

In this particular intensity scale, a [[Space (punctuation)|space character]] denoted an intensity between 0 and 1, that is between baseline and one standard deviation above it. The numbers 1 to 9 denoted the correspondingly numbered intensities (from 1 to 9); intensities of 10 and above were indicated by a letter: "A" corresponded to intensities between 10 and 11, "B" to 11 to 12, and so on. The Wow! signal's highest measured value was "U" (an intensity between 30 and 31), which is thirty standard deviations above background noise.<ref name="npr" /><ref name="code" />

=== Frequency ===
[[John Kraus]], the director of the observatory, gave a value of {{val|1420.3556|fmt=none|ul=MHz}} in a 1994 summary written for [[Carl Sagan]].<ref name=Kraus/> However, Ehman in 1998 gave a value of {{val|1420.4556|.005|fmt=none|u=MHz}}.<ref name="Big Ear 97">{{Cite web |last=Ehman |first=Jerry R. |date=February 3, 1998 |title=The Big Ear Wow! Signal. What We Know and Don't Know About It After 20 Years |url=http://www.bigear.org/wow20th.htm |access-date=July 2, 2016}}</ref> This is ({{val|50|5|u=kHz}}) above the [[hydrogen line]] value (with no [[Redshift|red-]] or blue-shift) of {{val|1420.4058|fmt=none|u=MHz}}. If due to blue-shift, it would correspond to the source moving about {{cvt|10|km/s}} towards Earth.

[[File:Wow signal spectrogram.svg|thumb|A [[heat map]] of the computer printout, giving a [[spectrogram]] of the beam; the Wow! signal appears as a bright spot in the lower left.]]
An explanation of the difference between Ehman's value and Kraus's can be found in Ehman's paper. The first [[local oscillator]] in the telescope's radio receiver was specified to a frequency value of {{val|1450.4056|fmt=none|u=MHz}}. However, the university's purchasing department made a [[typographical error]] in the order form, instead obtaining an oscillator with frequency {{val|1450.5056|fmt=none|u=MHz}} (i.e., {{val|0.1|u=MHz}} higher than desired). The software used in the experiment was then written to adjust for this error. When Ehman computed the frequency of the Wow! signal, he took this error into account.{{citation needed|date=August 2020}}

=== Bandwidth ===
The Wow! signal had a [[Bandwidth (signal processing)|bandwidth]] of less than {{val|10|u=kHz}}.  It is considered [[narrowband]] emission in the sense that its fractional bandwidth was relatively small (~1%).  However, the {{val|10|u=kHz}} bandwidth is not small compared to the bandwidth of some [[Maser#Astrophysical masers|astrophysical masers]] (~{{val|1|u=kHz}}) or to the frequency resolution of modern narrowband SETI searches (~{{val|1|u=Hz}}).<ref>{{Cite journal |last1=Margot |first1=Jean-Luc |last2=Pinchuk |first2=Pavlo |last3=Geil |first3=Robert |last4=Alexander |first4=Stephen |last5=Arora |first5=Sparsh |last6=Biswas |first6=Swagata |last7=Cebreros |first7=Jose |last8=Desai |first8=Sanjana Prabhu |last9=Duclos |first9=Benjamin |last10=Dunne |first10=Riley |last11=Lin Fu |first11=Kristy Kwan |last12=Goel |first12=Shashwat |last13=Gonzales |first13=Julia |last14=Gonzalez |first14=Alexander |last15=Jain |first15=Rishabh |display-authors=1 |date=6 January 2021 |title=A Search for Technosignatures around 31 Sun-like Stars with the Green Bank Telescope at 1.15–1.73 GHz |journal=[[The Astronomical Journal]] |volume=161 |issue=2 |pages=55 |arxiv=2011.05265 |bibcode=2021AJ....161...55M |doi=10.3847/1538-3881/abcc77 |s2cid=226290131 |doi-access=free |last16=Lam |first16=Adrian |last17=Lewis |first17=Briley |last18=Lewis |first18=Rebecca |last19=Li |first19=Grace |last20=MacDougall |first20=Mason |last21=Makarem |first21=Christopher |last22=Manan |first22=Ivan |last23=Molina |first23=Eden |last24=Nagib |first24=Caroline |last25=Neville |first25=Kyle |last26=O’Toole |first26=Connor |last27=Rockwell |first27=Valerie |last28=Rokushima |first28=Yoichiro |last29=Romanek |first29=Griffin |last30=Schmidgall |first30=Carlyn |last31=Seth |first31=Samar |last32=Shah |first32=Rehan |last33=Shimane |first33=Yuri |last34=Singhal |first34=Myank |last35=Tokadjian |first35=Armen |last36=Villafana |first36=Lizvette |last37=Wang |first37=Zhixian |last38=Yun |first38=In |last39=Zhu |first39=Lujia |last40=Lynch |first40=Ryan S.}}</ref> The Big Ear telescope was equipped with a receiver capable of measuring fifty {{val|10|u=kHz}}-wide channels. The output from each channel was represented in the computer printout as a column of alphanumeric intensity values. The Wow! signal is essentially confined to one column.<ref name="Big Ear 97" />

=== Time variation ===
At the time of the observation, the Big Ear radio telescope was only adjustable for [[Horizontal coordinate system|altitude]] (or height above the horizon), and relied on the [[rotation of the Earth]] to scan across the sky. Given the speed of Earth's rotation and the spatial width of the telescope's observation window, the Big Ear could observe any given point for just 72 seconds.<ref name="Skeptoid">{{Skeptoid |id=4342 |number=342 |title=Was the Wow! Signal Alien? |date=December 25, 2012 |access-date=October 8, 2016}}</ref> A continuous extraterrestrial signal, therefore, would be expected to register for exactly 72 seconds, and the recorded intensity of such signal would display a gradual increase for the first 36 seconds—peaking at the center of the observation window—and then a gradual decrease as the telescope moved away from it. All these characteristics are present in the Wow! signal.<ref name="edn">{{Cite web |last=Deffree |first=Suzanne |date=August 15, 2019 |title=Big Ear receives 'Wow! Signal,' August 15, 1977 |url=http://www.edn.com/electronics-blogs/edn-moments/4394137/Big-Ear-receives--Wow--Signal--August-15--1977 |access-date=July 2, 2016 |website=EDN Moments}}</ref><ref name="space_com">{{Cite news |last=Shostak |first=Seth |date=December 5, 2002 |title=Interstellar Signal From the 70s Continues to Puzzle Researchers |url=http://www.bigear.org/shostak_wow_20021205.htm |access-date=July 2, 2016 |work=Space.com}}</ref>