About a week ago, Joe Taylor posted a message about the FT2 “developments”.
Citation:
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.
Hmm, our Italian team “invented” a new Decodium version on the 8th of March, now advertising a asynchronous mode.
It seems to me that the people behind Decodium were “inspired” by the suggested development by Joe and Claude AI must have had a busy few days to “develop” this new version.
Again, it looks like another attempt to get attention, but probably without any serious theoretical considerations.
As written in a previous post, pursuing speed comes at a cost: protocols become more critical. There is a huge amount of protocols for wireless (or wired) communication. Each protocol is designed for specific purposes and designs take many aspects into account, like available spectrum, propagation, interference etc.
The JT modes can be seen as a slow time division multiplex access (TDMA) system, with predefined slots. Collision detection is not part of the protocol. Most collisions occur in pile-ups for a DXpedition, but are in sync with each other. Receivers know when transmissions (approximately) start.
Asynchronous modes introduce additional complexity, because collisions are more likely and transmissions no longer take place in fixed time slots. Where DXpeditions now usually transmit during even periods, with asynchronous modes, this is no longer true.
CW of SSB (expedition) stations can work split to avoid collisions of callers with their transmissions, but unless the digital protocol supports (forced) split, callers will interfere with the expedition. Congestion will slow down things exponentially.
On VHF bands, like 50 MHz, mutual interference between nearby stations can be avoided by transmitting during the same period, but that is impossible with asynchronous modes.
As explained here, decoding requires time and the on air listening test revealed that decoding was often (too) slow and led to repeats. It is likely that the Decodium team learned from the “beta test” that this aspect is a serious disadvantage. Asynchronous communication can resolve this, because the receiving station can finish decoding before the next transmission. Well, problem solved then?
Collisions are likely to be a kill factor, especially on a busy band.
By the way, the Decodium web site now claims that FT2 can average periods and gain sensitivity. It made me smile. Even with 4 periods, it cannot beat FT8… and is not faster.
If we go back to the original announcement: “The fastest mode”, it looks like Mother Nature reminds us about laws of physics.