WSJT-X version 2.4.0 has introduced a new digital protocol called Q65, which is designed for “minimal two-way QSOs over especially difficult propagation paths,” the Quick start guide" says.
“On paths with Doppler spread more than a few hertz, the weak-signal performance of Q65 is the best among all WSJT-X modes. Q65 is particularly effective for tropospheric scatter, ionospheric scatter, and EME on VHF and higher bands, as well as other types of fast-fading signals.”
The new protocol uses 65-tone frequency-shift keying and builds on the demonstrated weak-signal strengths of QRA64, introduced in 2016. User messages and sequencing are identical to those in FT4, FT8, FST4, and MSK144. Q65 employs a “unique tone” to sync time and frequency. “As with JT65, this ‘sync tone’ is readily visible on the waterfall spectral display,” the Guide said. “Unlike JT65, synchronization and decoding are effective even when meteor pings or other short signal enhancements are present.
Transmit/receive sequence lengths of 15, 30, 60, 120, and 300 seconds are available. According to the Guide, “Q65 will enable stations with a modest Yagi and 100 W or more and to work one another on 6 meters at distances up to ~1600 kilometers at most times, in dead band conditions.”
Information from arrl.org
Quick-Start Guide to Q65 Steve Franke, K9AN; Nico Palermo, IV3NWV; Bill Somerville, G4WJS; and Joe Taylor, K1JT December 10, 2020 WSJT-X 2.4.0 will introduce Q65, a digital protocol designed for minimal two-way QSOs over especially difficult propagation paths. On paths with Doppler spread more than a few Hz, the weaksignal performance of Q65 is the best among all WSJT-X modes. Q65 is particularly effective for tropospheric scatter, ionospheric scatter, and EME on VHF and higher bands, as well as other types of fast-fading signals. Q65 uses 65-tone frequency-shift keying and builds on the demonstrated weak-signal strengths of QRA64, a mode introduced to WSJT-X in 2016. Q65 differs from QRA64 in the following important ways: • A new low-rate Q-ary Repeat Accumulate code for forward error correction • User messages and sequencing identical to those in FT4, FT8, FST4, and MSK144 • A unique tone for time and frequency synchronization. As with JT65, this “sync tone” is readily visible on the waterfall spectral display. Unlike JT65, synchronization and decoding are effective even when meteor pings or other short signal enhancements are present. • Optional submodes with T/R sequence lengths 15, 30, 60, 120, and 300 s. • A new, highly reliable list-decoding technique for messages that contain previously copied message fragments. Basic parameters of Q65 for each of the five T/R sequence lengths are summarized in the table below. Threshold sensitivities (SNR in 2500 Hz bandwidth yielding 50% probability of decode) were measured for each submode using simulations over the additive white Gaussian noise (AWGN) channel. As with other recently developed modes in WSJT-X, a feature called a priori (AP) decoding improves sensitivity by several additional dB as information is accumulated during a standard minimal QSO.
“On paths with Doppler spread more than a few hertz, the weak-signal performance of Q65 is the best among all WSJT-X modes. Q65 is particularly effective for tropospheric scatter, ionospheric scatter, and EME on VHF and higher bands, as well as other types of fast-fading signals.”
The new protocol uses 65-tone frequency-shift keying and builds on the demonstrated weak-signal strengths of QRA64, introduced in 2016. User messages and sequencing are identical to those in FT4, FT8, FST4, and MSK144. Q65 employs a “unique tone” to sync time and frequency. “As with JT65, this ‘sync tone’ is readily visible on the waterfall spectral display,” the Guide said. “Unlike JT65, synchronization and decoding are effective even when meteor pings or other short signal enhancements are present.
Transmit/receive sequence lengths of 15, 30, 60, 120, and 300 seconds are available. According to the Guide, “Q65 will enable stations with a modest Yagi and 100 W or more and to work one another on 6 meters at distances up to ~1600 kilometers at most times, in dead band conditions.”
Information from arrl.org
Quick-Start Guide to Q65 Steve Franke, K9AN; Nico Palermo, IV3NWV; Bill Somerville, G4WJS; and Joe Taylor, K1JT December 10, 2020 WSJT-X 2.4.0 will introduce Q65, a digital protocol designed for minimal two-way QSOs over especially difficult propagation paths. On paths with Doppler spread more than a few Hz, the weaksignal performance of Q65 is the best among all WSJT-X modes. Q65 is particularly effective for tropospheric scatter, ionospheric scatter, and EME on VHF and higher bands, as well as other types of fast-fading signals. Q65 uses 65-tone frequency-shift keying and builds on the demonstrated weak-signal strengths of QRA64, a mode introduced to WSJT-X in 2016. Q65 differs from QRA64 in the following important ways: • A new low-rate Q-ary Repeat Accumulate code for forward error correction • User messages and sequencing identical to those in FT4, FT8, FST4, and MSK144 • A unique tone for time and frequency synchronization. As with JT65, this “sync tone” is readily visible on the waterfall spectral display. Unlike JT65, synchronization and decoding are effective even when meteor pings or other short signal enhancements are present. • Optional submodes with T/R sequence lengths 15, 30, 60, 120, and 300 s. • A new, highly reliable list-decoding technique for messages that contain previously copied message fragments. Basic parameters of Q65 for each of the five T/R sequence lengths are summarized in the table below. Threshold sensitivities (SNR in 2500 Hz bandwidth yielding 50% probability of decode) were measured for each submode using simulations over the additive white Gaussian noise (AWGN) channel. As with other recently developed modes in WSJT-X, a feature called a priori (AP) decoding improves sensitivity by several additional dB as information is accumulated during a standard minimal QSO.