[ADXA] Joe Taylor's explanation of "FT2"

[Charles McKenzie]

There have been some FT2 operations on 14.094 , while it is quick, my observations are the sensitivity is not there compared to ft8 or 4. I wasn’t very impressed. But who am I to say!
73
KF5TL
Sent from my iPhone

On Mar 4, 2026, at 6:56 PM, WB5JJJ <wb5jjj at gmail.com> wrote:


The name FT2 was first used for a ham radio digi-mode in January 2019, when Steve Franke (K9AN), Bill Somerville (G4WJS), and I were exploring possible digital modes that might plausibly become popular for ham radio contesting. In addition to timed-sequence modes like
speeded-up versions of FT8, we considered asynchronous modes similar to traditional RTTY, but offering far lower error rates and much better weak-signal performance.

We implemented test protocols of both synchronous and asynchronous types, using different original codecs and digital modulation ranging from 2-tone minimum shift keying (MSK) to 4-tone Gaussian-shaped frequency shift keying (4-GFSK). We tested these modes on the air with a range of speeds, including full transmissions as short as 2.5 s conveying two callsigns plus a grid locator, signal report, or contest exchange. We explored the loss of effective throughput of each experimental mode on a wide range of simulated ionospheric propagation channels.

With the help of a number of contest-oriented beta testers, we arranged mock-contest practice sessions, testing one asynchronous mode and several synchronous modes with different T/R cycle lengths. The testing group's overall judgment was that timed-sequence modes faster than 7.5 s do not leave enough time for operator judgment and interaction. They necessarily require levels of automation that obviate the desirable contesting emphasis on operating skill and making good strategic decisions. In June 2019 we settled on the protocol specification that became FT4. It was released as part of WSJT-X 2.1.0 on July 15, 2019. I consider FT4 to be a moderately successful mode, but even for contesting it has not replaced (or even caught up to) FT8 in popularity.

Despite what you may have read (e.g., "This innovative protocol was developed from scratch by Martino (IU8LMC) and the ARI Caserta Team"), the mode recently being called "FT2" is nothing more than FT4 sent at twice the speed. Indeed, the "FT2" offered by DG2YCB in an experimental "WSJT-X i+" version uses the exact FT4 software and simply scales the generated and received waveforms by a factor of 2.

Compared with FT4, "FT2" is significantly less sensitive, needs twice the bandwidth, and has far more decoding failures caused by timing errors. The mode is hardly usable without full (or nearly full) automation. We have no plan to add a twice-speeded-up version of FT4 in the mainline program WSJT-X. We are, however, experimenting with a possible asynchronous mode that would be operationally more like traditional RTTY. It's too soon to say when (or if) it might be released for wider testing.

-----

73's
George - WB5JJJ
HoIP - 100105
Cell - 479.857.7737
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