This is an old revision of this page, as edited by David Biddulph (talk | contribs) at 06:52, 30 January 2022 (→Controversy: {{unsourced section|date=January 2022}}). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.
Revision as of 06:52, 30 January 2022 by David Biddulph (talk | contribs) (→Controversy: {{unsourced section|date=January 2022}})(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)FT8 is a popular amateur radio digital mode. The most widely used FT8 software is WSJT-X. It is widely used on the shortwave (high frequency/HF) bands. The exchange consists of call signs, signal-to-noise ratios, and Maidenhead Locator System grid squares.
Joe Taylor, K1JT, announced on June 29, 2017, the availability of FT8 in WSJT-X. FT8 stands for "Franke-Taylor design, 8-FSK modulation" and was created by Joe Taylor, K1JT and Steve Franke, K9AN. It is described as being designed for "multi-hop Es where signals may be weak and fading, openings may be short, and you want fast completion of reliable, confirmable QSO's".
According to Taylor, the important characteristics of FT8 are —
- T/R sequence length: 15 s
- Message length: 75 bits + 12-bit CRC
- FEC code: (174,87) LDPC
- Modulation: 8-FSK, keying rate = 6.25 baud; tone spacing = 6.25 Hz
- Waveform: Continuous phase, constant envelope
- Occupied bandwidth: 50 Hz
- Synchronization: three 7x7 Costas arrays (start, middle, end of transmission)
- Transmission duration: 79*1920/12000 = 12.64 s
- Decoding threshold: -24 dB (with decoding)
- Operational behavior: similar to HF usage of JT9, JT65
- Multi-decoder: finds and decodes all FT8 signals in passband
- Auto-sequencing after manual start of QSO
Compared to the so-called "slow modes" (JT9, JT65, QRA64), FT8 is a few decibels less sensitive, but allows completion of QSOs four times faster. Bandwidth is greater than JT9, but about one-quarter of JT65A and less than one-half of QRA64. Compared with the "fast modes" (JT9E-H), FT8 is significantly more sensitive, has much narrower bandwidth, uses the vertical waterfall, and offers multi-decoding over the full displayed passband.
Controversy
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FT8 is somewhat controversial, with some amateur radio operators having strong opinions either for or against its use. Some common claims in favor of its use are that it reduces the barrier to entry of amateur radio by making inefficient antennas (which are more feasible for use in apartments and under many other circumstances) and low-power transceivers (which are often less expensive than higher-power transceivers), while its opponents often claim that it is "ruining ham radio" or other phrases expressing a belief that use of FT8 is contrary to the purposes of amateur radio.
References
- "FT8 Mode is Latest Bright Shiny Object in Amateur Radio Digital World". American Radio Relay League (ARRL). 2017-08-01.
- Joe Taylor, K1JT. "FT8".
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