Amateur Television: Getting Started With ATV and DATV

Most radio amateurs know voice, Morse and data modes. Far fewer have tried to send live video, yet amateur television is one of the oldest and most rewarding branches of the hobby. A camera, a transmitter on a microwave-friendly band and a simple receiver are enough to show a friend across the valley what your hands are doing at the bench, to share a view from a balloon or a rocket, or to run a club demonstration that people remember. The field has changed a lot in recent years. Analog television, which needed several megahertz of bandwidth and a lot of power, has been joined by digital amateur television, which uses the same modulation as satellite television, works with much less power and is built on cheap hardware. This guide explains the options and how to start.

What Amateur Television Is

Amateur television, usually shortened to ATV, means the transmission of moving pictures and sound by radio amateurs on the bands where the rules allow it. The overview of amateur television describes its history and its different forms. Video needs far more bandwidth than voice, so ATV is found on the upper bands, usually 70 centimetres and above, where there is enough space. In practice, the most common bands are 70 centimetres, 23 centimetres, 13 centimetres and 3 centimetres, together with the satellite links described below.

Because the signals are wide, ATV is a line-of-sight activity at normal power, and range depends on height and the antenna, as our article on the basics of VHF and UHF operating explains. Distances of tens of kilometres are common with modest equipment and good antennas, and many clubs run ATV repeaters that relay pictures from a hilltop.

Analog and Digital Amateur Television

There are two families of ATV, and the choice affects everything you buy.

Analog ATV

Analog ATV uses the same kind of signal as old broadcast television. On 70 centimetres, it is often amplitude modulated with a vestigial sideband, with a bandwidth of about 6 to 7 MHz. On 23 centimetres and higher bands, frequency modulation is common, with a wide bandwidth of 15 MHz or more. The pictures are simple to generate with a camera and a transmitter, the receivers are cheap and the delay is short, which suits live demonstrations and fast-moving scenes. The disadvantages are the width of the signal, which limits the number of channels, and the fact that the picture degrades slowly as the signal weakens, which means snow and noise.

Digital ATV

Digital ATV, often called DATV, encodes the video and uses a digital modulation, commonly the DVB-S or DVB-S2 standard that is used by satellite television. The signal can be much narrower, from a few hundred kilohertz to a few megahertz depending on the symbol rate and the picture quality. The picture is either clean or gone, with little in between, but it holds on weaker signals than analog and it is more efficient in bandwidth. Digital transmitters can be built from inexpensive software defined radio modules and a small computer, and receivers are often low-cost satellite television tuners or an SDR. The main disadvantage is a delay of a fraction of a second to a second, caused by encoding and decoding.

Comparing the Options

The table summarises the main differences, so you can pick the approach that fits your station.

If you have a friend nearby with analog equipment, you may start there, but most new activity is digital, and DATV repeaters and satellite use are growing.

What You Need for a First Station

A basic digital ATV station has four elements, and a basic analog station needs the same ones in simpler form.

1. A camera and a microphone. Any camera with a video output, a webcam or a camera on a small computer will do. Good lighting improves the picture more than a more expensive camera.
2. An encoder and modulator. For DATV, this is usually an SDR transmitter or a dedicated board driven by software. A number of projects use a Raspberry Pi, and the British Amateur Television Club offers designs and software through its website.
3. A power amplifier and filter. Many low-power modules produce only milliwatts. An amplifier brings the level to a few watts, and a band-pass or low pass filter ensures that harmonics do not leave your station. Our guide on low pass filters explains why this matters.
4. An antenna and feed line. A directional antenna such as a Yagi or a dish gives the best results. At 23 centimetres and above, cable loss is severe, so keep the feed line short and use a quality type.

On the receive side, you need an antenna, a low-noise preamplifier if the path is long, a tuner or SDR with demodulation software and a display. The receive chain is often the cheaper half.

Choosing a Band

The band determines the antennas, the cable loss and the other stations that you can reach. The 70 centimetre band is shared with many other services, and signals are wide, so check your national band plan and the local ATV channels. The 23 centimetre band offers more space and better antenna gain for a given size, but cable loss is higher, and the band is shared with other users, so the channel choice matters. At 13 centimetres and above, a small dish gives great gain, and line of sight becomes critical. Our 70 centimetre band guide covers the equipment and propagation on the lower of the two bands, which is a good place to begin.

For satellite use, the geostationary QO-100 transponder offers a wideband channel that carries digital amateur television between stations in a large part of the world. Our article on QO-100 describes the equipment, which includes a small dish and a converter. The wideband transponder is one of the easiest ways to send DATV over very long distances, with no need for a tower or a hilltop.

Your First Picture

Start simple and build up. The first goal is to send a picture across the room, and then across the street, before attempting a long path.

1. Connect the camera to the encoder, set the resolution to a modest value and confirm that you see a picture on the local monitor.
2. Connect a dummy load or an attenuator to the transmitter output and check the signal with a receiver at close range.
3. Choose a frequency within the band plan and a symbol rate that suits the path. A lower symbol rate gives a narrower signal and a longer range, but a lower picture quality.
4. Add the callsign to the picture as an on-screen text overlay. Identification is required, and it also helps other stations.
5. Connect the antenna, move to a clear spot and test with a friend, with both stations pointing at each other.
6. Improve the path step by step, by raising the antenna, shortening the cable and adding a preamplifier at the receiver.

Take notes of the settings for each test, because the combination of symbol rate, error correction and picture size has a large effect on both range and quality.

Receiving and Reporting

Many people start on the receive side, because it is cheap and needs no licence. A DVB-S receiver, a low-noise block or preamplifier and an antenna are enough to watch repeaters and other stations in range. The quality of the received picture depends mainly on the signal margin, which is the difference between the signal level and the minimum that the demodulator needs. Most demodulators display a margin or a modulation error ratio, and watching this value while you move the antenna is the quickest way to improve the path. If you see the picture freeze or break into blocks, you are close to the edge, and a few decibels of gain from a better antenna or a shorter cable will restore it.

When you contact another station, report more than the word “picture”. Give the signal margin in decibels if your receiver shows it, the symbol rate in use and a short description of what you see, such as blocking, freezing or a clean picture. These details help the other operator to adjust the settings, and they make your own experiments repeatable. Over a few weeks of tests, you will build up a personal table of what works for each path, and that knowledge is the real reward of the mode.

Operating Practice and Rules

Amateur television follows the same principles as every other mode. Identify with your callsign, stay within the limits of your licence and the band plan, and listen before you transmit. The wide signal means that you can easily overlap other activity, so choose channels that are in use for ATV in your region, and avoid frequencies reserved for weak-signal work. Check your national regulations on the allowed power and bandwidth, and on content, since commercial or broadcast content is not allowed. Most clubs and the national societies publish local ATV channel lists.

Be thoughtful about interference. A wide signal on 70 centimetres can disturb other users, including repeaters and satellite links, if it is poorly filtered or too strong. Use only as much power as you need, and keep the antenna pointed at the other station and not into a neighbourhood. For a general overview of the issue, the guide to RF exposure and safety is a good complement, because microwave antennas with high gain concentrate power in a narrow beam.

Projects That Use ATV

Video opens the door to projects that are difficult with voice or data. A camera in a weather balloon payload sends live views of the curvature of the earth. A camera on a model rocket or an aircraft gives a first-person view, though you must follow the rules for the vehicle. A club can send a live picture of a field day station to a display at a public event. A repeater that shows the view from a mountain gives a weather camera for the whole region. And a simple link between the shack and the workshop shows a friend how to hold the iron while soldering. Each of these builds skill in antennas, amplifiers and filters in addition to video.

Common Mistakes

• Starting with a long path. Test across the room and across the street first.
• Using too much power. A clean low-power signal often works better than a distorted high-power one.
• Forgetting the filter. Wide, amplified signals produce harmonics that can disturb others.
• Using long, thin cable at 23 centimetres. The loss can be larger than the gain of the antenna.
• Not identifying. Add a text overlay with the callsign to every picture.

The Bottom Line

Amateur television is accessible to anyone with an interest in radio and a little patience. Analog ATV is simple and immediate, while digital ATV gives better range for the bandwidth and is where most development is happening. Begin with a short test across the room, add a filter and an amplifier, choose a band in line with your band plan, and move to longer paths with a directional antenna. When you are ready for something bigger, try a repeater, a club event or a satellite link. The first live picture from your own station is a memorable moment.

Frequently Asked Questions

What is the difference between ATV and DATV?

ATV usually means analog television, with wide signals and a gradual loss of quality. DATV is the digital version, which uses narrower signals and a picture that is either clear or lost.

Which bands are used for amateur television?

Most activity is on 70 centimetres, 23 centimetres, 13 centimetres and 3 centimetres, together with wideband satellite channels. Check your own band plan and licence for the allowed segments.

Do I need a special licence?

Television is generally allowed under an ordinary amateur licence on the bands that permit it, but the details differ by country, so check your national rules before transmitting.

How much power do I need?

Digital ATV works with a few watts or less on short paths. Longer paths benefit more from a directional antenna and a low-loss cable than from extra power.

Can I send ATV through a satellite?

Yes. The wideband transponder on the QO-100 geostationary satellite carries digital amateur television and can be reached with a small dish and a suitable converter.

What do I need to receive ATV?

An antenna, a low-noise amplifier on long paths, and a receiver such as an SDR or a satellite television tuner with software to demodulate the signal and display the picture.