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ft8 [2026/10/02 16:22] – Organise Wikiham as an encyclopedia of individual articles 127.0.0.1ft8 [2026/10/02 21:06] (current) – Add technical encyclopedia coverage, formulas, examples and primary references admin
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 ====== FT8 ====== ====== FT8 ======
  
-**FT8** is a structured, short-message digital mode used in amateur radio. It is available in the WSJT-X software suite and is designed for weak-signal communication.+**FT8** is a structured weak-signal digital mode for short amateur radio contacts. Its name refers to Franke–Taylor design work and eight frequency states. It is implemented in WSJT-X and related software, including the CB-oriented [[wsjt_cb|WSJT-CB]] fork. 
 + 
 +===== Protocol ===== 
 + 
 +FT8 alternates transmit and receive opportunities in **15-second slots**. A standard transmission contains 79 symbols: 58 carry encoded data and 21 form synchronisation sequences. 
 + 
 +^ Parameter ^ Value ^ 
 +| Modulation | Eight-tone Gaussian frequency-shift keying | 
 +| Symbol rate | 6.25 baud | 
 +| Tone spacing | 6.25 Hz | 
 +| Approximate occupied bandwidth | 50 Hz | 
 +| Message payload | 77 bits | 
 +| Error protection | 14-bit CRC and (174,91) LDPC coding | 
 + 
 +<code> 
 +On-air symbol duration = 79 / 6.25 = 12.64 s 
 +</code> 
 + 
 +The on-air duration and the 15-second slot are different. Remaining time supports the timing and processing needed for an exchange. 
 + 
 +===== Messages and reports ===== 
 + 
 +Common messages exchange callsigns, a Maidenhead locator, a signal report and acknowledgements such as RRR or RR73. Structured encoding uses the limited payload efficiently; free text and non-standard identifiers have their own constraints. 
 + 
 +Reports express signal-to-noise ratio relative to a **2500 Hz reference bandwidth**. A negative report is compatible with reception because the decoder uses a much narrower signal and coding. It should not be compared directly with an unrelated receiver meter reading. 
 + 
 +Non-standard callsigns may use hashes. A listener can see an unresolved identifier until a later message supplies the mapping. This is different from losing every part of the contact.
  
 ===== Station setup ===== ===== Station setup =====
  
-A typical station combines a transceiver, a computer and an audio or data interface. Audio levels, transmit control, frequency settings and time synchronisation are part of the setup.+A station needs accurate time, stable tuning, correct audio devices and suitable transmit control. In [[single_sideband|USB]], audio offset contributes to the actual transmitted RF frequency; the dial alone does not identify the centre of every trace.
  
-Consult the documentation for the installed WSJT-X version when configuring a station or interpreting a decoded message.+Excessive drive or clipping can create unwanted emissions. Observe the radio's cooling and duty-cycle limits, and check received messages throughout an automatic sequence. One decode is not evidence that both stations completed a contact.
  
 ===== See also ===== ===== See also =====
  
 +  * [[ft4|FT4]]
   * [[digital_mode|Digital mode]]   * [[digital_mode|Digital mode]]
-  * [[amateur_radio_operating|Amateur radio operating]]+  * [[decibel|Decibel]] 
 +  * [[wspr|WSPR]]
  
 ===== References ===== ===== References =====
  
-  * [[https://wsjt.sourceforge.io/wsjtx.html|WSJT-X project and documentation]]+  * [[https://wsjt.sourceforge.io/FT4_FT8_QEX.pdf|Franke, Somerville and Taylor: FT4 and FT8 communication protocols]]. 
 +  * [[https://wsjt.sourceforge.io/wsjtx.html|WSJT-X project and current user documentation]].