Ch 37 is used by radio astronomers for observations. Since they are measuring very weak signals, it is important that there are no transmissions (even part 15 is banned) on these frequencies (608-614 mHz).
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Channel 37 is an unused television channel in countries using the M and N broadcast television system standards. Channel 37 occupies a band of UHF frequencies from 608 to 614 MHz, frequencies that are particularly important to radio astronomy because they allow observations at a frequency between the dedicated frequency allocations near 410 MHZ and 1400 MHZ. One radio astronomy application in this band is for Very-long-baseline interferometry. [1] In 1963, when there were very few stations in the UHF band, the US Federal Communications Commission (FCC) adopted a 10-year moratorium on any allocation of stations to Channel 37. A new ban on such stations took effect at the beginning of 1974, and was made permanent by a number of later FCC actions. As a result of this, and similar actions by the Canadian Radio-television and Telecommunications Commission, Channel 37 has never been used by any over-the-air television station in Canada or the United States.
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from:
http://en.wikipedia.org/wiki/Channel_37
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