American Radio Relay League (ARRL)

ARRL logo type_17_6The American Radio Relay League (ARRL) is the largest membership association of amateur radio enthusiasts in the USA. ARRL is a non-profit organization, and was founded in 6th April 1914 by Hiram Percy Maxim of Hartford, Connecticut. The ARRL represents the interests of amateur radio operators before federal regulatory bodies, provides technical advice and assistance to amateur radio enthusiasts, supports a number of educational programs and sponsors emergency communications service throughout the country. The ARRL has approximately 154,000 members. In addition to members in the US, the organization claims over 7,000 members in other countries. The ARRL publishes many books and a monthly membership journal called QST. The ARRL held its Centennial Convention in Hartford, Connecticut in July 2014.

The ARRL is the primary representative organization of amateur radio operators to the US government. It performs this function by lobbying the US Congress and the Federal Communications Commission. The ARRL is also the international secretariat of the International Amateur Radio Union, which performs a similar role internationally, advocating for amateur radio interests before the International Telecommunications Union and the World Administrative Radio Conferences.

The organization is governed by a member-elected, volunteer Board of Directors. Each director serves a three-year term and represents the members within their particular region of the country. The national headquarters facilities are located in Newington, Connecticut. Along with the administrative headquarters, the 7-acre (2.8 ha) site is home to amateur radio station W1AW. The ARRL Field Organization carries out local and regional activities across the United States.

Paul Leicester | MØFOX | Chesterfield UK | IO93HE | Icom IC-7300

SSTV Slow Scan TV

The concept of SSTV was introduced by Copthorne Macdonald [1] in 1957–1958.[2] He developed the first SSTV system using an electrostatic monitor and a vidicon tube. In those days it seemed sufficient to use 120 lines and about 120 pixels per line to transmit a black-and-white still picture within a 3 kHz phone channel. First live tests were performed on the 11 Meter ham band – which was later given to the CB service in the US. In the 1970s, two forms of paper printout receivers were invented by hams.

Early usage in space exploration

Astronaut Gordon Cooper, SSTV broadcast from Faith 7
SSTV was used to transmit images of the far side of the Moon from Luna 3.[3]

The first space television system was called Seliger-Tral-D and was used aboard Vostok. Vostok was based on an earlier videophone project which used two cameras, with persistent LI-23 iconoscope tubes. Its output was 10 frames per second at 100 lines per frame video signal.
The Seliger system was tested during the 1960 launches of the Vostok capsule, including Sputnik 5, containing the space dogs Belka and Strelka, whose images are often mistaken for the dog Laika and the 1961 flight of Yuri Gagarin, the first man in space on Vostok 1.
Vostok 2 and thereafter used an improved 400-line television system referred to as Topaz.
A second generation system (Krechet, incorporating docking views, overlay of docking data, etc.) was introduced after 1975.

A similar concept, also named SSTV, was used on Faith 7 as well as on the early years of the NASA Apollo program. The Faith 7 camera transmitted one frame every two seconds.

NASA slow scan image from the Moon.
The Apollo TV cameras used SSTV to transmit images from inside Apollo 7, Apollo 8, and Apollo 9, as well as the Apollo 11 Lunar Module television from the Moon. NASA had taken all the original tapes and erased them for use on subsequent missions; however, the Apollo 11 Tape Search and Restoration Team formed in 2003 tracked down the highest quality footage among the converted recordings of the first broadcast, pieced together the best footage, then contracted a specialist film restoration company to enhance the degraded black-and-white film and convert it into digital format for archival records.[4]
The SSTV system used in NASA’s early Apollo missions transferred ten frames per second with a resolution of 320 frame lines using less bandwidth than a normal TV transmission.
The early SSTV systems used by NASA differ significantly from the SSTV systems currently in use by amateur radio enthusiasts today.


Commercial systems started appearing in the United States in 1970, after the FCC had legalized the use of SSTV for advanced level amateur radio operators in 1968.

SSTV originally required quite a bit of specialized equipment. Usually there was a scanner or camera, a modem to create and receive the characteristic audio howl, and a cathode ray tube from a surplus radar set. The special cathode ray tube would have “long persistence” phosphors that would keep a picture visible for about ten seconds.

The modem would generate audio tones between 1200 and 2300 Hz from picture signals, and picture signals from received audio tones. The audio would be attached to a radio receiver and transmitter.

Current systems

A modern system, having gained ground since the early 1990s, uses a personal computer and special software in place of much of the custom equipment. The sound card of a PC, with special processing software, acts as a modem. The computer screen provides the output. A small digital camera or digital photos provide the input.


SSTV uses analogue frequency modulation, in which every different value of brightness in the image gets a different audio frequency. In other words, the signal frequency shifts up or down to designate brighter or darker pixels, respectively. Color is achieved by sending the brightness of each color component (usually red, green and blue) separately. This signal can be fed into an SSB transmitter, which in part modulates the carrier wave.

There are a number of different modes of transmission, but the most common ones are Martin M1 (popular in Europe) and Scottie S1 (used mostly in the USA).[5] Using one of these, an image transfer takes 114 (M1) or 110 (S1) seconds. Some black and white modes take only 8 seconds to transfer an image.


A calibration header is sent before the image. It consists of a 300-millisecond leader tone at 1900 Hz, a 10 ms break at 1200 Hz, another 300-millisecond leader tone at 1900 Hz, followed by a digital VIS (vertical interval signaling) code, identifying the transmission mode used. The VIS consists of bits of 30 milliseconds in length. The code starts with a start bit at 1200 Hz, followed by 7 data bits (LSB first; 1100 Hz for 1, 1300 Hz for 0). An even parity bit follows, then a stop bit at 1200 Hz. For example, the bits corresponding the decimal numbers 44 or 32 imply that the mode is Martin M1, whereas the number 60 represents Scottie S1.

Slow scan Test card
A transmission consists of horizontal lines, scanned from left to right. The color components are sent separately one line after another. The color encoding and order of transmission can vary between modes. Most modes use an RGB color model; some modes are black-and-white, with only one channel being sent; other modes use a YC color model, which consists of luminance (Y) and chrominance (R-Y and B-Y). The modulating frequency changes between 1500 and 2300 Hz, corresponding to the intensity (brightness) of the color component. The modulation is analogue, so even though the horizontal resolution is often defined as 256 or 320 pixels, they can be sampled using any rate. The image aspect ratio is conventionally 4:3. Lines usually end in a 1200 Hz horizontal synchronization pulse of 5 milliseconds (after all color components of the line have been sent); in some modes, the synchronization pulse lies in the middle of the line.


Below is a table of some of the most common SSTV modes and their differences.[5] These modes share many properties, such as synchronization and/or frequencies and grey/color level correspondence. Their main difference is the image quality, which is proportional to the time taken to transfer the image and in the case of the AVT modes, related to synchronous data transmission methods and noise resistance conferred by the use of interlace.

SSTV Slow Scan TV

Paul Leicester | MØFOX | Chesterfield UK | IO93HE | Icom IC-7300

MØFOX UK Ham Radio

MØFOX Amateur Radio Website – Paul Leicester

Amateur radio (also called ham radio) is the use of designated radio frequency spectra for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication. The term “amateur” is used to specify persons interested in radio technique solely with a personal aim and without direct monetary or other similar reward, and to differentiate it from commercial broadcasting, public safety (such as police and fire), or professional two-way radio services (such as maritime, aviation, taxis, etc.).

The amateur radio service (amateur service and amateur satellite service) is established by the International Telecommunication Union (ITU) through the International Telecommunication Regulations. National governments regulate technical and operational characteristics of transmissions and issue individual stations licenses with an identifying call sign. Prospective amateur operators are tested for their understanding of key concepts in electronics and the host government’s radio regulations. Radio amateurs use a variety of voice, text, image, and data communications modes and have access to frequency allocations throughout the RF spectrum to enable communication across a city, region, country, continent, the world, or even into space.

Amateur radio is officially represented and coordinated by the International Amateur Radio Union (IARU), which is organized in three regions and has as its members the national amateur radio societies which exist in most countries. According to an estimate made in 2011 by the American Radio Relay League, two million people throughout the world are regularly involved with amateur radio.[1] About 830,000 amateur radio stations are located in IARU Region 2 (the Americas) followed by IARU Region 3 (South and East Asia and the Pacific Ocean) with about 750,000 stations. A significantly smaller number, about 400,000, are located in IARU Region 1 (Europe, Middle East, CIS, Africa).

M0FOX UK Ham Radio

Paul Leicester | MØFOX | Chesterfield UK | IO93HE | Icom IC-7300