Amateur television
Amateur television (ATV) is the transmission of
ATV is an extension of amateur radio. It is also called HAM TV or fast-scan TV (FSTV), as opposed to slow-scan television (SSTV).
North America
In
Most ATV signals are transmitted in either
2 m band
The 2-meter band (144-148 MHz) lies within cable channel 18, but at 4 MHz wide, it is too narrow to fit the full 6 MHz bandwidth of an NTSC analog channel; its audio carrier lies outside the band. To be used as a television frequency, some narrow-bandwidth format incompatible with most televisions must be used and converted.
The 2-meter band is often used by ATV operators for coordination with each other via FM voice transmissions. Operators seeking an ATV contact might first attempt calling on a regionally recognized ATV liaison-frequency, commonly 144.34 MHz, then agree to an ATV frequency to use for the video transmissions. The 2 meter frequency may be used throughout the contact to talk back to the current station transmitting video. The receiving station(s) may suggest adjustments the sending station can make, such as antenna direction, to improve the quality of the video received.
70 cm band
The
Additionally, this band can be easily received by simply tuning any cable-ready analog television or cable-box to the cable TV channels below and connecting an outdoor TV antenna. Amateur TV signals are much weaker than broadcast TV, so a preamplifier is often used to improve reception.
Analog (IRC) channel |
Channel Bandwidth (MHz) | Video Freq (MHz) | Audio Freq (MHz) | Notes |
---|---|---|---|---|
57 | 420–426 | 421.25 | 425.75 | 1,2 |
58 | 425–431 | 426.25 | 430.75 | 1,3 |
58 | 426–432 | 427.25 | 431.75 | 1 |
59 | 432–438 | 433.25 | 437.75 | |
59 | 432.75–438.75 | 434.00 | 438.50 | 3 |
60 | 438–444 | 439.25 | 443.75 | 6 |
61 | 444–450 | 445.25 | 449.75 | 4 |
Usage notes:
- In Canada and areas of the US north of a designated "Line A" boundary, amateurs are not allowed to transmit on these channels.[5][6][7]
- Usually used as an ATV repeater output. VSB filters must be used on this channel to keep the signal inside the ham band.
- Channels 58 and 59 are often offset in frequency to limit interference to the weak-signal and amateur radio satellitesub-bands (431–433 & 435–438 MHz respectively). Many modern CATV receivers can still lock-on to frequencies offset as much as 1 MHz.
- Rarely used today due to heavy FM repeater use in this range.
- To remain within the amateur radio bandwidth allocation, a maximum of two channels may be simultaneously used within a given geographic area, and the video carrier frequencies must be at least 12 MHz apart for the signals not to interfere with each other.
- May not be used within 160 kilometers of Joint Base Cape Cod to protect PAVE PAWS.[8][9]
33 cm band
The
These channels can be received by many newer analog cable-boxes and televisions, which can tune to channels above 125.
Analog (IRC) channel |
Channel Bandwidth (MHz) | Video Freq (MHz) | Audio Freq (MHz) | Notes |
---|---|---|---|---|
143 | 906–912 | 907.25 | 911.75 | 1 |
N/A | 909–915 | 910.25 | 914.75 | |
N/A | 910–916 | 911.25 | 915.75 | |
144 | 912–918 | 913.25 | 917.75 | |
145 | 918–924 | 919.25 | 923.75 | |
N/A | 922–928 | 923.25 | 927.75 | 2,3 |
Usage notes:
- Available, but no known usage.
- In portions of Colorado and Wyoming, amateurs are not allowed to transmit ATV on this channel.[11]
- May interfere with growing FM use on the 927–928 MHz sub-band.
- For technical reasons, a maximum of two channels may be simultaneously used within a given geographic area, and the video carrier frequencies must be at least 12 MHz apart for the signals not to interfere with each other.
Additionally 33 cm is the lowest frequency band on which higher-quality
23 cm band
The
Commonly used 23 cm FM channels:
- 1,255 MHz
- 1,265 MHz
This band is also used for AM/VSB television, although this requires a specialized receiver.
Channel Bandwidth (MHz) | Video Freq (MHz) | Audio Freq (MHz) | Notes |
---|---|---|---|
1,240 – 1,246 | 1,241.25 | 1,245.75 | 1 |
1,252 – 1,258 | 1,253.25 | 1,257.75 | 3 |
1,264 – 1,270 | 1,265.25 | 1,269.75 | |
1,276 – 1,282 | 1,277.25 | 1,281.75 | |
1,288 – 1,294 | 1,289.25 | 1,293.75 |
Usage notes:
- VSB filters must be used on this channel to keep the signal inside the ham band.
- All of the video carrier frequencies are 12 MHz apart to allow for each channel to be used simultaneously in a given geographic area without causing interference to each other.
- Not available in certain New England states due to interference with the FAA's surveillance radar at Cummington, Massachusetts.[13]
Other amateur radio bands
In addition to the above, there are other ham bands which are less commonly used for ATV:
- On the 13-centimeter band:
- 2,417.5 MHz is used for ATV links.
- 2,441.5 MHz is the band's most used FM ATV frequency. A 6.0 MHz audio sub-carrierand 4 MHz deviation are used.
- The 9 centimeter (3 GHz) and 5 centimeter (5 GHz) bands have ATV links in some areas.
- On the 3-centimeter band, 10.4 GHz is a wideband FM channel, and it may be used as an ATV repeater input.
Other information
The distance record for ATV is between Hawaii and California (2,518 miles) on 434 MHz.[14]
Experiments with
There is now a DATV downlink on the ISS operating in the amateur 2.4 GHz band. The QO-100 geostationary satellite wideband transponder has DATV uplinks in the 2.4 GHz and downlinks in 10 GHz amateur bands.
Europe
In
In several countries
In the
Transmission characteristics
Typically
on the four channels listed above.In a nutshell
The quality of transmission is expressed as a "p level"; "p" standing for "picture". P levels range from zero to five, increasing as the picture becomes more viewable. P-0 signifies a state in which sync bars are visible, but the picture is too snowy to be seen; this occurs at a minimum signal strength of 3 dB. Each level represents an increase of 6 dB over the previous; P-5 is 30 dB above P-0 and represents a perfectly clear picture.[16]
Range
As transmission frequency increases, atmospheric
Content
Content produced by ATV has included:
- From 1968 to about 2004 amateur TV provided behind-the-scenes co-ordination for the annual New Year's Day Tournament of Roses Paradein Pasadena, California.
- Ham TV (as it is also called) provides video co-ordination of many public service events and, along with traditional amateur radio, provides "eyes" in natural disasters.
- U.S. stations often retransmitted work of the United States government, has no copyright and can be legally and freely retransmitted without permission, and has the advantage of not having to be manually programmed by the amateur station itself. In a similar vein, other public domain filler content can include television episodes and films with expired copyrights—especially silent filmsin scenarios where content without audio is needed—with the caveat that this content must be programmed.
- In recent history, amateur TV has found renewed interest in the radio-controlled hobby world as a method for transmitting FPV video, for use when flying remote control aircraft or piloting other RC vehicles.
See also
- ATSC Standards
- DVB-T
- NTSC
- SECAM
- SSTV
- Narrow-bandwidth television
References
- ^ "United Kingdom Frequency allocation table" (PDF). Publication date 2008 (Issue No. 15). Ofcom. Archived from the original (PDF) on 17 January 2011. Retrieved 26 November 2010.
- ^ Kowalewski, Anthony, "An Amateur's Television Transmitter" Archived 2011-09-24 at the Wayback Machine, Radio News, April 1938. Early Television Museum and Foundation Website. Retrieved 19 July 2009.
- ^ "HF - Propagation Predictions from the United Kingdom". Publication date November 2010. Radio Society of Great Britain. Archived from the original on 24 October 2010. Retrieved 26 November 2010.
- ^ Neuhaus, John (2005-10-19). "Cable TV Channel Frequencies". John Neuhaus. Retrieved 2009-05-06.
- ^ Line A is defined in the US Federal Code of Regulations Part 47,[1] and runs from Aberdeen, Washington to Searsport, Maine, roughly parallel to the Canada–US border in several segments.
- ^ ITU Radio Regulations, Volume 1 (PDF) (2012, Volume 1 ed.). International Telecommunication Union. 2012. p. 38. Archived from the original (PDF) on 28 July 2017. Retrieved 21 February 2016.
- ^ "Frequency Coordination with Canada Below 470 MHz". Federal Communications Commission. 2016-01-27. Retrieved 2022-05-07.
- ^ PavePAWS 160km protection zone from the Connecticut Spectrum Management Agency's website, retrieved December 28, 2019.
- ^ New England Spectrum Management Agency bandplan, including 440 MHz; retrieved December 28, 2019.
- ^ ITU Radio Regulations, Volume 1 (PDF) (2012, Volume 1 ed.). International Telecommunication Union. 2012. pp. 96–98. Archived from the original (PDF) on 28 July 2017. Retrieved 21 February 2016.
- ^ 47 C.F.R. §97.303(n)3 as of 14 Feb 2011
- ^ "Welcome to Amateur Tv".
- ^ NEAMC bandplans; retrieves December 28, 2019.
- ^ "ATV W6ORG - ATV DX Records".
- ^ "Amateur Television in Central Ohio". ATCO. Archived from the original on 27 April 2009. Retrieved 2009-05-06.
- ^ "ATV P level illustration". Archived from the original on 2009-06-17. Retrieved 2009-06-14.
- ISBN 0-87259-928-0.