Amateur television (ATV) is the transmission of
broadcast quality video
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) sy ...
and
audio
Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to:
Sound
*Audio signal, an electrical representation of sound
*Audio frequency, a frequency in the audio spectrum
* Digital audio, representation of sou ...
over the wide range of frequencies of
radio wave
Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz ( GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (sho ...
s allocated for
radio amateur (Ham) use. ATV is used for
non-commercial
A non-commercial (also spelled noncommercial) activity is an activity that does not, in some sense, involve commerce, at least relative to similar activities that do have a commercial objective or emphasis. For example, advertising-free community ...
experimentation, pleasure, and public service events. Ham TV stations were on the air in many cities before
commercial television
Commercial broadcasting (also called private broadcasting) is the broadcasting of television programs and radio programming by privately owned corporate media, as opposed to state sponsorship. It was the United States′ first model of radio (a ...
stations came on the air. Various transmission standards are used, these include the broadcast transmission standards of
NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
in
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
and
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
, and
PAL or
SECAM
SECAM, also written SÉCAM (, ''Séquentiel de couleur à mémoire'', French for ''color sequential with memory''), is an analog color television system that was used in France, some parts of Europe and Africa, and Russia. It was one of th ...
elsewhere, utilizing the full
refresh rates of those standards. ATV includes the study of building of such
transmitter
In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...
s and
receivers, and the study of
radio propagation
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere.
As a form of electromagnetic radiation, like light waves, radio waves are affect ...
of signals travelling between transmitting and receiving stations.
ATV is an extension of
amateur radio
Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency commu ...
. It is also called HAM TV or fast-scan TV (FSTV), as opposed to
slow-scan television (SSTV).
North America
In
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
,
amateur radio bands that are suitable for a television signal (
wide
WIDE or Wide may refer to:
*Wide (cricket)
*Wide and narrow data, terms used to describe two different presentations for tabular data
*WIDE Project, Widely Integrated Distributed Environment
*Wide-angle Infinity Display Equipment
*WIDE-LP, a radio ...
enough to fit such a signal) are higher in frequency than VHF broadcast TV. The lowest frequency ham band suitable for television transmission is
70 centimeters, which is between broadcast channels 13 and 14. While outside of broadcast television channels, this frequency falls into
CATV frequencies
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is e ...
, on channels 57 to 61
(IRC) (420–450
MHz). As such, ATV transmissions can be viewed by setting a television or analog cable-box to cable input and attaching an outdoor antenna. For more sensitive reception, some users may use a purposely-built ATV down-converter, which is a kind of
set-top-box. Other bands are also used for ATV, most of them in the
UHF
Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...
region on frequencies higher than UHF broadcast TV.
33 centimeters and
23 centimeters are two other commonly used bands for ATV, but reception of these higher bands requires the use of a down-converter.
Most ATV signals are transmitted in either
amplitude modulation (AM) or
vestigial sideband (VSB) NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
(North American analog TV broadcast modulation standard). DSB AM and VSB AM signals are inherently compatible with each other, and most televisions can receive either. DSB-AM signals consists of the carrier and both upper and lower sidebands. VSB-AM is where DSB-AM is filtered and the lower sideband is highly attenuated at frequencies more than 1.25 MHz from the carrier signal. A VSB filter can be added to a DSB-AM transmitter to make it a VSB signal. The filters, depending on power usage, will cost anywhere from US$100–1,000. For practical reasons, most individual ATV users transmit in DSB-AM, and VSB is transmitted by repeater stations. On the 33 cm and higher bands,
frequency modulation (FM) ATV may be used, and on the
SHF and
EHF ham bands, FM is more commonly used than VSB or AM. FM ATV is incompatible with AM/VSB ATV, and a separate
demodulator
Demodulation is extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated ...
, such as an analog satellite receiver, is necessary to receive signals.
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
70-centimeter band
The 70-centimeter or 440 MHz band is a portion of the UHF radio spectrum internationally allocated to amateur radio and amateur satellite use. The ITU amateur radio allocation is from 430 to 440 MHz; however, some countries, such as the Unit ...
(420-450 MHz) is the most commonly used ham band for ATV. Signals transmitted on this band usually propagate longer distances than on higher frequency bands, for a given transmitter power and antenna gain. The band falls between
broadcast TV channels 13 and 14, which are 210–216 MHz and 470–476 MHz respectively. Propagation is similar to the lowest UHF TV broadcast channels.
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
A preamplifier, also known as a preamp, is an electronic amplifier that converts a weak electrical signal into an output signal strong enough to be noise-tolerant and strong enough for further processing, or for sending to a power amplifier a ...
is often used to improve reception.
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.
# 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 satellite sub-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
PAVE PAWS ( PAVE Phased Array Warning System) is a complex Cold War early warning radar and computer system developed in 1980 to "detect and characterize a sea-launched ballistic missile attack against the United States". With the first solid-s ...
.
33 cm band
The
33-centimeter band (902-928 MHz) is next highest frequency ham band available for ATV in North America. This ham band is unique to
ITU Region 2, and it is rarely available for amateur use in ITU Regions 1 or 3.
This band is also shared with many users, including
ISM devices and unlicensed
Part 15 users, so interference issues are more likely than on other bands.
These channels can be received by many newer analog cable-boxes and televisions, which can tune to channels above 125.
Usage notes:
# Available, but no known usage.
# In portions of
Colorado
Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...
and
Wyoming
Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to t ...
, amateurs are not allowed to transmit ATV on this channel.
# 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
frequency modulated amateur TV occurs. This format gives better picture quality than standard AM television. The FM television format used is identical to
big dish analog satellite television and can be received by some tuners which can tune this low in frequency. Otherwise a specialized FM amateur TV receiver is needed.
23 cm band
The
23-centimeter band (1240-1300 MHz) is the third highest frequency band available for ATV. Analog big-dish satellite television (
TVRO) receivers may be re-purposed for inexpensively receiving ATV in this band. Such receivers can decode FM television when an outdoor antenna is connected to the
LNB input. Due to the low cost and ease of repurposing old analog satellite receivers, this is the most popular band for FM amateur TV.
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.
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.
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-carrier
A subcarrier is a sideband of a radio frequency carrier wave, which is modulated to send additional information. Examples include the provision of colour in a black and white television system or the provision of stereo in a monophonic radio broa ...
and 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.
Experiments with
digital modes have lagged somewhat behind those in Europe, but have taken on some new urgency given the
transition of broadcast television. WR8ATV currently has an output using
DVB-S
Digital Video Broadcasting – Satellite (DVB-S) is the original DVB standard for Satellite Television and dates from 1995, in its first release, while development lasted from 1993 to 1997. The first commercial applications was by Star TV in Asia ...
, which is believed to be the first DATV repeater in the US.
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
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
, which generally has a narrower
70 cm
The 70-centimeter or 440 MHz band is a portion of the UHF radio spectrum internationally allocated to amateur radio and amateur satellite use. The ITU amateur radio allocation is from 430 to 440 MHz; however, some countries, such as the Unit ...
allocation than the USA, the majority of amateur television operation is currently
frequency modulated on and above. The frequencies in use depend on national permissions. In most of mainland Europe, the most common frequency is 1255 MHz. Other bands commonly used for ATV are the
13cm () and
3-cm () bands, although ATV is used on most of the microwave bands.
In several countries
cross-band repeater
In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Som ...
s are used, with
AM inputs on 430 MHz and
FM outputs on , others have FM-ATV inputs on and outputs on .
In the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and ...
, much activity occurs using
in-band
In telecommunications, in-band signaling is the sending of control information within the same band or channel used for data such as voice or video. This is in contrast to out-of-band signaling which is sent over a different channel, or even ...
repeater
In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Som ...
s. These generally have an input of 1248, 1249 or 1255 MHz and typically output at 1308, 1312 or 1316 MHz, although other frequencies are also used.
Simplex
In geometry, a simplex (plural: simplexes or simplices) is a generalization of the notion of a triangle or tetrahedron to arbitrary dimensions. The simplex is so-named because it represents the simplest possible polytope in any given dimension. ...
operation occurs on these or other frequencies chosen to avoid interference with other users of the band, e.g. . Recent
experiment
An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs whe ...
s have been done with
digital
Digital usually refers to something using discrete digits, often binary digits.
Technology and computing Hardware
*Digital electronics, electronic circuits which operate using digital signals
** Digital camera, which captures and stores digital ...
modes following widely adopted
DVB-S
Digital Video Broadcasting – Satellite (DVB-S) is the original DVB standard for Satellite Television and dates from 1995, in its first release, while development lasted from 1993 to 1997. The first commercial applications was by Star TV in Asia ...
and
DVB-T
DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in Feb ...
standards. These new DATV transmissions need less spectrum bandwidth than FM-ATV and offer superior picture quality. However, the unavoidable processing delays caused by the temporal compression mean that DATV signals have a second or more of time lag, which can make real-time video conversations feel much less natural than the 'instantaneous' analogue system.
Transmission characteristics
Typically
frequency modulated TV is used on frequencies above 1,240 MHz (1.24
GHz), where there is enough
bandwidth for such
wideband
In communications, a system is wideband when the message bandwidth significantly exceeds the coherence bandwidth of the channel. Some communication links have such a high data rate that they are forced to use a wide bandwidth; other links ma ...
transmission
Transmission may refer to:
Medicine, science and technology
* Power transmission
** Electric power transmission
** Propulsion transmission, technology allowing controlled application of power
*** Automatic transmission
*** Manual transmission
** ...
s. This is often used as a repeater's input
frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
, with output being standard
VSB on the four channels listed above.
In a nutshell
* below 1.24 GHz: Vestigial Sideband
* above 1.24 GHz:
FM,
PSK etc...
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.
Range
As transmission frequency increases, atmospheric
path losses become greater, particularly at frequencies above 10 GHz. Additionally, long-distance propagation by
F-layer ionospheric skip over the horizon does not typically occur at higher frequencies, and terrain and man-made structures can affect propagation of signals, blocking or redirecting signals. Factors such as
E-layer skip propagation,
tropospheric enhancement, and
knife-edge diffraction can extend the useful range of signals.
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 Parade
A tournament is a competition involving at least three competitors, all participating in a sport or game. More specifically, the term may be used in either of two overlapping senses:
# One or more competitions held at a single venue and concentr ...
in 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
NASA TV while they were not in use, especially when there were
Space Shuttle
The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program n ...
missions. NASA TV, as a
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
The public domain (PD) consists of all the creative work to which no exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly waived, or may be inapplicable. Because those rights have expired ...
filler content can include television episodes and
films with expired copyrights—especially
silent film
A silent film is a film with no synchronized recorded sound (or more generally, no audible dialogue). Though silent films convey narrative and emotion visually, various plot elements (such as a setting or era) or key lines of dialogue may, w ...
s in 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
Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like th ...
*
DVB-T
DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in Feb ...
*
NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
*
SECAM
SECAM, also written SÉCAM (, ''Séquentiel de couleur à mémoire'', French for ''color sequential with memory''), is an analog color television system that was used in France, some parts of Europe and Africa, and Russia. It was one of th ...
*
SSTV
*
Narrow-bandwidth television Narrow-bandwidth television (NBTV) is a type of television designed to fit into a channel narrower than the standard bandwidth used for official television standards.
The three predominant worldwide broadcast television standards use either 6 ...
References
External links
List of european stations
*
British Amateur Television Club
{{Telecommunications
Amateur radio
Television terminology