Channel 37

Channel 37 is a purposefully unused television channel in countries using the M and N broadcast television system standards. The frequency region set aside for Radio Astronomy is really from 600 MHz (0.5m) to 620 MHz (0.4835m) -- but the area reserved or unused differs from nation to nation and region to region (as for example the EU and British Isles have slightly different reserved frequency areas).

Channel 37 in System M & N countries specifically occupies a band of UHF frequencies from 608 to 614 MHz. This band is particularly important to radio astronomy because it allows observation in a region of the spectrum in between the dedicated frequency allocations near 410 MHz and 1.4 GHz.

One radio astronomy application in this band is for very-long-baseline interferometry.

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.

Some nations, for whatever reason may not only fail to set aside this region for Radio Astronomy -- but may outright allot broadcasters channels in this spectrum region. In New Zealand (as of 2016), Maori Television has been given 2 channel allotments nationwide in this frequency region.

Reservations and use outside the US have a non-exclusive legal status

Since July 2000, Channel 37 may also be used in the US for medical telemetry equipment on a co-primary basis. This equipment must emit no more than one watt of effective radiated power, and is for use in hospitals and other such facilities.

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