FT8

It’s still in beta test­ing, but FT8 — the lat­est dig­i­tal bauble to cap­ture the imag­i­na­tion of the Ama­teur Radio com­mu­ni­ty — has been lur­ing away many of those already using the pop­u­lar JT65 “weak-sig­nal” mode. FT8 is includ­ed in a beta release of WSJT‑X, ver­sion 1.8.0‑rc1. Among its biggest advan­tages is a short­er trans­mit-receive cycle, mean­ing quick­er con­tacts. The notes for the “can­di­date” release say that FT8 offers “sen­si­tiv­i­ty down to –20 dB on the AWGN chan­nel.” Con­tacts are four times faster than with JT65 or JT9, and an entire FT8 con­tact can take place in about 1 minute.

The new mode is named after its devel­op­ers, Steven Franke, K9AN, and Joe Tay­lor, K1JT. The numer­al des­ig­nates the mode’s 8‑frequency shift key­ing for­mat. Tones are spaced at 6.25 Hz, and an FT8 sig­nal occu­pies just 50 Hz. Unlike JT65 or JT9, trans­mit and receive cycles in FT8 each last about 15 sec­onds. Like JT65, FT8 requires accu­rate time syn­chro­niza­tion. An auto-sequenc­ing fea­ture offers the option to respond auto­mat­i­cal­ly to the first decod­ed reply to your CQ.

FT8 is an excel­lent mode for HF DXing and for sit­u­a­tions like mul­ti-hop Es on 6 meters, where deep QSB may make fast and reli­able com­ple­tion of QSOs desir­able,” Taylor’s release notes assert.

The beta release came out just days before the July CQ VHF Con­test and proved to be a boon to many oper­a­tors who took advan­tage of FT8 on 6 meters. In a lim­it­ed out­ing for the CQ VHF, Frank Dono­van, W3LPL, made 22 FT8 con­tacts on 6 meters, “dur­ing which the FT8 soft­ware report­ed SNRs from my receiv­er below –10 dB (mea­sured in a 2,500-Hz band­width). Some of the 22 QSOs may have been dif­fi­cult to com­plete on CW.”

Enthu­si­asts will have to wait a lit­tle longer for Log­book of The World (LoTW) to accept FT8 con­tacts as FT8 con­tacts. Because FT8 is still in beta, it has not yet been added to the ADIF tables. Con­fig­ur­ing TQSL to auto­mat­i­cal­ly map FT8 con­tacts to “DATA” will enable users to upload FT8 con­tacts now, and con­fir­ma­tions will be valid for DXCC Dig­i­tal, VUCC, WAS Dig­i­tal, and WPX Dig­i­tal awards. A new TQSL con­fig­u­ra­tion will be released once the new mode has been accept­ed to ADIF, which could hap­pen with­in a week.

Oper­a­tional doc­u­men­ta­tion for FT8 has not yet been final­ized. “We know that the advent of new mode FT8 means that new mate­r­i­al is need­ed for the User Guide,” Tay­lor told the Yahoo Mete­or Scat­ter and Weak Sig­nal Group this week. “We will be work­ing on that in the near future.”

 

From  ARRL

Joe Tay­lor, K1JT, announced on June 29, 2017 the avail­abil­i­ty of a new mode in the WSJT‑X soft­ware, FT8FT8 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 J. Tay­lor, the impor­tant char­ac­ter­is­tics of FT8 are:

T/R sequence length: 15 s
Mes­sage length: 75 bits + 12-bit CRC
FEC code: LDPC(174,87)
Mod­u­la­tion: 8‑FSK, key­ing rate = tone spac­ing = 6.25 Hz
Wave­form: Con­tin­u­ous phase, con­stant enve­lope
Occu­pied band­width: 50 Hz
Syn­chro­niza­tion: three 7×7 Costas arrays (start, mid­dle, end of Tx)
Trans­mis­sion dura­tion: 79×1920÷12000 = 12.64 s
Decod­ing thresh­old: ‑20 dB (per­haps ‑24 dB with a pri­ori decod­ing, TBD)
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 dB less sen­si­tive but allows com­ple­tion of QSOs four times faster. Band­width is greater than JT9, but about 14 of JT65A and less than 12 QRA64. Com­pared with the fast modes (JT9E‑H), FT8 is sig­nif­i­cant­ly more sen­si­tive, has much small­er band­width, uses the ver­ti­cal water­fall, and offers mul­ti-decod­ing over the full dis­played pass­band. Fea­tures not yet imple­ment­ed include sig­nal sub­trac­tion, two-pass decod­ing, and use of a pri­ori (already known) infor­ma­tion as it accu­mu­lates dur­ing a QSO.”

From  WSJT


Comments are closed.

Solar-Terrestrial Data


Geomagnetic Field status monitor

Solar X-rays:

Geomagnetic Field:
>
Status
Status
 
From n3kl.org

Recent Comments


    Archives


    Categories