FT8

FT8 is a popular form of digital weak signal communication used primarily by amateur radio operators to communicate on amateur radio bands with a majority of traffic occurring on the HF amateur bands. The mode offers operators the ability to communicate despite unfavorable conditions such as those seen during low solar activity, high RF noise, or with low transmitter power. With advances in signal processing technology, software can decode FT8 signals with a signal-to-noise ratio as low as −20 dB in a 2500 Hz bandwidth, which is significantly lower than conventional CW or SSB transmissions. ==Operation==

FT8 involves 77-bit message blocks transmitted in regular 15-second periods, consisting of 12.64 seconds of transmission time and 2.36 seconds of decode time, giving a digital data rate of 6.09 bits/sec. Source encoding gives an effective message throughput equivalent to about 5 words per minute. The required signal-to-noise ratio in a 2500 Hz bandwidth is −21 dB, so the corresponding Eb/N0 is 10 log10(2500/6.09) = 26.1 dB greater, or −21 dB + 26.1 = 5.1 dB. Applications There are multiple uses for FT8 including contesting, testing antennas, and for scientific research. == Applications in amateur radio ==

In amateur radio, FT8 is a mainstream digital modulation mode. It operates on a 15-second cycle, usually completing a QSO in about 90 seconds. It’s commonly used for short-wave QSOs, DX, and long-distance contacts. Most amateur radio hobbyists monitor FT8 frequencies on the HF bands. During meteor scatter or sporadic-E propagation, FT8 signals can sometimes be received from over 1000 km away. To avoid interference and maintain reliable operation, hams have designated specific FT8 frequencies in each amateur band. Common short-wave frequencies include 7.074 MHz (40 m), 14.074 MHz (20 m), 21.074 MHz (15 m), and 28.074 MHz (10 m). Format and requirements FT8 communication requires strict time accuracy. Each transmission must begin exactly at 00, 15, 30, 45, or 60 seconds. If the station clock is not properly synchronized, messages will likely fail to decode. FT8 has 6 stages, usually like this. == References ==