Understandably, a number of people have asked us about how SuperFox
works. I have explained that we are intentionally moving slowly and
deliberately in our early tests, and we have not published source code
or specifications in part because many details may still change.
The basic SuperFox scheme has been proven to work well. It delivers the
promised weak-signal gain of around 10 dB over multi-streaming FT8 with
5 streams. The present scheme will certainly be used for the Jarvis
Island operations next month, but a variety of things could change after
that.
Our goals for design of a SuperFox mode have included the following:
1. Constant envelope waveform, and hence up to 10 dB signal-strength
improvement over multi-streamed FT8.
2. Anti-piracy feature: a way to establish legitimacy of signal origin.
3. A way to prevent (or make much more difficult) misuse or our
technology by derivative or modified programs, for example enabling
robotic strings of QSOs.
4. Better use of available bandwidth: Fox should use (say) at least half
of a ~3 kHz slice.
5. Better immunity to QRM, including deliberate QRM.
6. Operational aids for the Fox operator, including longer free text
messages.
As you can see, technical details have been important in our planning
but sociological, moral, and even legal issues are involved as well.
Objective 2 in the above list involves cyber security matters, an area
in which we have little expertise. Our weak-signal performance
requirements demand small message payloads, and these are incompatible
with (for example) most public/private key schemes.
For nearly all of its 24 year history the WSJT project has been entirely
open source. Ideally we'd like to keep it that way. But objective 3 in
the list is especially difficult (and likely impossible) to achieve in a
fully open source project.
We appreciate all the help we have received in testing an early SuperFox
scheme. We hope many will work a new one when N5J operates as SuperFox
from Jarvis Island. We'll continue working toward a maxmially effective
SuperFox design in the presence of many challenges, including possible
software licensing issues, and we welcome all constructive input from
other interested hams. As always, our efforts are intended to benefit
the wonderful hobby we share.
-- 73, Joe, K1JT
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