Channel 37 is a purposefully unused UHF television broadcasting television channel in the United States, Canada and Mexico. The frequency range allocated to this channel is important for radio astronomy, so broadcasting is not licensed.
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. 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).
When UHF channels were being allocated in the United States in 1952, channel 37 was assigned to 18 communities across the country. One of them, Valdosta, Georgia, featured the only construction permit ever issued for channel 37: WGOV-TV, owned by Eurith Dickenson "Dee" Rivers Jr., son of the former governor of Georgia (hence the call letters). Rivers received the CP on February 26, 1953, but WGOV-TV never made it to the air; on October 28, 1955 they requested an allocation on channel 8, but the petition was denied.
In 1963, the 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.
Reservations and use outside the US have a non-exclusive legal status
- The Canadian Radio-television and Telecommunications Commission (CRTC) enacted such a ban on Channel 37, but Radio Astronomy has no Exclusive Status on this channel.
- Mexico observes a similar ban on the use of this TV channel, but the allocation, like Canada's, is not exclusive.
- Guatemala has a ban on Channel 37.
- Most NTSC System-M countries have an informal ban on Channel 37 as well, but don't give radio astronomy exclusive use of the channel.
Since July 2000, Channel 37 may 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.
- The power level permitted by the FCC is many times more than the amount allowed for Part 15 unlicensed broadcasting.
- In US areas set aside for radio-frequency silence, this equipment is banned by statute and regulation.
- This seemingly low power level can be troublesome for radio astronomy equipment, which depends on detecting extraordinarily low signal strengths. Any use of the same frequencies raises the noise floor, thereby decreasing the signal-to-noise ratio, and making the work more difficult.
Channel 1 was also removed from the TV bandplan in the late 1940s, channels 70 to 83 (800 MHz band) by the 1980s mainly for AMPS mobile phones and, in June 2009, channels 52 to 69 (700 MHz band) for mobile phones, emergency services and mobile TV services such as Qualcomm's now-defunct MediaFLO (channel 55). Additional channels from 38 to 51 (600 MHz band) are being taken away from TV broadcasters after FCC auction 1000 ended in early 2017, which will leave channel 37 as a guard band between repacked TV stations and more mobile networks, for which T-Mobile USA won most of the licenses.
Certain channels, 14 through 20, are used for land mobile communications in some large metropolitan areas in the U.S. However, facilities using this decades-old co-allocation are just treated as another station to avoid interference to in their local area.
The channels displayed by cable converter boxes under these numbers are not on the same frequencies as their over-the-air counterparts; there are also virtual channel numbering schemes in use in digital television which do not map directly to fixed frequency channel assignments. As such, a "cable 37" channel may (and most often does) exist, but on a much lower frequency.
Outside North America
In NTSC-M countries
Outside North America, channel 37 is actively used in these countries where NTSC-M is used:
- In the Philippines, Channel 37 was used by UNTV-37 in Metro Manila as Progressive Broadcasting Corporation's analog channel. However, its digital broadcast assignment is on Channel 38 (ISDB-T). It is used by ABS-CBN TV-3 in Cebu City, Cebu as ABS-CBN's digital channel (ISDB-T). However, its analog broadcasts primarily on Channel 3. It is used by ABS-CBN TV-10 in Iloilo City, Iloilo as ABS-CBN's digital channel (ISDB-T). However, its analog broadcasts primarily on Channel 10. Also used by GMA TV-5 in Davao as GMA Network's digital channel (ISDB-T). However, its analog broadcasts primarily on Channel 5.
- in Trinidad and Tobago, WIN-TV is broadcast on Channels 37 and 39, using NTSC
- In the Dominican Republic channel 37 is also used for the CDN news channel
- In South Korea KBS 2TV's Analog channel on gwanak-san Transmission station.(01.Jan.2012 04:00 closed.)
In other countries
In these other countries, the frequency allocation for these TV channels is different:
- in the UK (many transmitters used by the Five network actually broadcast on channel 37)
- in Western Europe, Channel 37 is used fairly widely as a relay transmitter frequency.
- In Malaysia, NTV7 broadcasts in PAL on CCIR Channel 37 (599.25 MHz)
Channel 37 is not the same frequency as it is in the countries using the System-M/N standard. At least in the UK, 606–614 MHz is reserved for radio astronomy.
The UK's namesake "Channel 37", while different in frequency, was formerly part of a small group of channels reserved for non-broadcast purposes such as RF modulators in video players. The UK-named 34-37 channel range is no longer reserved in this manner.
Global UHF TV allocation table (605–615 MHz)
This Radio Astronomy Allocation is between the following wavelengths:
- 605 MHz = 0.49552 m = 49.55 cm
- 615 MHz = 0.48747 m = 48.75 cm
- Assume either a 100 kHz or a 250 kHz guardband with respect to this allocation.
DVB-T adoption note : The tables above are not accurate for nations that have adopted DVB-T. The frequencies for audio and video are merged with DVB terrestrial television. The new DVB frequencies are rounded off to an even number in MHz as a general rule.
National arrangements for radio astronomy different from ITU-R
National arrangements for radio astronomy different from ITU-R Radio Regulations
Central & Western Europe
- Austria: no allocation - only mention of No. 5.149
- Bulgaria: no allocation
- Belgium: assignment to radio astronomy (shared with active services)
- Finland: no allocation
- Estonia: no allocation
- Iceland: no allocation
- Liechtenstein: no allocation
- Luxembourg: no allocation
- Netherlands: primary status
- Portugal: no allocation
- Spain: no allocation
- Sweden: no allocation
- United Kingdom: no reference to No. 5.149
Rest of World
- Armenia: no allocation
- Russian Federation: no allocation
- Turkey: no allocation
- New Zealand, Maori TV and others (not allocated to Radio Astronomy at all)
As national (and ITU) frequency allocations can have multiple users (or no users at all) there should be some disambiguation as to what the various kinds of allocation schemes are
- No Allocation and Primary Status could be considered equivalent legal status. Very often the lack of allocation implies an internal regulatory coherence with ITU-R regulations freeing up this band for Astronomy.
- Assignment and Primary Status could be considered equivalent legal statuses as well.
- FCC database for Channel 37, had shown possible usage conflict with Mexico but now has the channel entirely clear in Canada, the U.S.A. & Mexico.
- US FCC's attack on Channel 37
- W9Wi.com: An article about channel 37 and channels above 69
- craf.eu: Astrophysical importance of the band 608 - 614 MHz
- Spare That Channel, Time, 10 May 1963
- FREQUENCIES ALLOCATED TO RADIO ASTRONOMY USED BY THE DSN
- McAdams On: Channel 37
Rest of World