Click on the images for a full-size view.

All the samples shown on this page have been received using FTV. Images have been cropped to speed up page loading.

WEFAX consists of photographic imagery transmitted by weather satellites. The image opposite shows the western part of the mediterranean sea. It was received from a low orbiting NOAA weather satellite.

HFFAX consists of high resolution charts from terrestrial facsimile stations, text and photographic images relayed from weather satellites. A few press stations also transmit newsprint and press photographs.

SSTV stands for Slow Scan Television, which consists of still images. SSTV images are exchanged by radio amateurs over long distances, using terrestrial radio as well as amateur radio satellites.

RTTY stands for radio teletype, which is text by radio. It is transmitted asynchronously using FSK, typically with a shift of 170 Hz at speeds of 45, 50, 75 or 100 baud. The screenshot shows FTV receiving RTTY in a DOS window.

SITOR stands for simplex teletype over radio. It is similar to RTTY but implements error correction. SITOR-A uses Automatic Repeat Request (ARQ) and is used for point-to-point links. It has a characteristic chirping sound. SITOR-B uses Forward Error Correction (FEC) and is used for broadcasts.

NAVTEX is part of the Global Maritime Distress Safety System (GMDSS), supplying shipping with weather reports and navigational warnings. NAVTEX is broadcast on 518 kHz using SITOR-B at 100 baud.

Data analysis functions such as Mark to space ratio, Symbol width and Auto-correlation function (ACF) facilitate the identification of the many different signals encountered on the air waves. The examples below show the results from an analysis of a NAVTEX signal.