“All fast modes in WSJT-X send their message frames repeatedly, as many times as will fit into the sequence length,” he explained.Ĭompared with FT8, FT4 is 3.5 dB less sensitive and requires 1.6 times the bandwidth, but it offers the potential for twice the contact rate. Taylor noted that even with their shorter transmit-receive sequences, FT4 and FT8 are considered “slow modes,” because their message frames are sent only once per transmission. “FT4 is faster still (7.5-second T/R sequences) and especially well suited for contesting.”
“FT8 is operationally similar but four times faster (15-second T/R sequences) and less sensitive by a few decibels,” developer Joe Taylor, K1JT, explains in the version 2.2.0 User Guide. JT65 and QRA64 were designed for EME (“moonbounce”) on VHF/UHF bands but have also proven very effective for worldwide very low-power communication on HF bands. The first six are designed for reliable contacts under weak-signal conditions, and they use nearly identical message structure and source encoding. WSJT-X version 2.2 offers 10 different protocols or modes - FT4, FT8, JT4, JT9, JT65, QRA64, ISCAT, MSK144, WSPR, and Echo. WSJT-X version 2.2.0 is now in general availability release, after a short stint in beta (or release candidate) status.
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