[SFDXA] SuperFox - Interesting Conversation regarding Reception/Propagation

[Bill]

/From WSJTx Improved list:

/Seeing how SuperFox occupies 1.5 kHz bandwidth vs. 50 Hz for a Fox 
(normal) stream, how much more vulnerable is the new SuperFox mode to 
interference (intentional or otherwise)?

It would be interesting to know what simulations have been done to 
investigate the different possible impacts caused by the propagation 
itself as well as by man made noise and what the results have been. When 
I look at the difficult reception of K8K in Germany in FT8 from time to 
time (polar path with a lot of flutter) even with acceptable signal 
strenghts I wonder how the signals from Jarvis can be decoded in 
Germany. But let us see.

Regarding the 10 dB system gain compared to standard fox: Is there 
somebody in the group who can explain or give me some information how 
this has been calculated? We can do this off-list because this is 
somehow quite specific and not so interesting for the majority of the 
users here.

Despite my above comments/questions: I still believe that the new mode 
has many advantages when I look at Uwe's list, so this new mode could be 
another nice step forward. But we should know the trade offs as well.,73 
Juergen, DL8LE


Hello Jürgen,
Firstly, this already results from theoretical considerations. Joe 
answered a similar question on the WSJT GROUP forum as follows:

/FT8 transmissions, and each stream of old-style Fox transmissions, each 
convey a 77-bit payload.    Necessarily, when multiple streams are used 
the 1/N^2 law is in effect and signal strength is reduced.//
//
//SuperFox transmissions do not use "streams", and they always convey a 
payload of 319 bits. For one QSO at a time FT8 is more efficient, and 
uses much less bandwidth.  But for many simultaneous QSOs the SuperFox 
approach (wider bandwidth, a highly effective Q-ary polar code, 128-FSK 
constant envelope modulation) wins by a large margin. /

Then there have been of course a number of comparative tests (mostly 
performed by Steve K9AN or Joe). If I remember correctly, the results 
showed a system gain of between 9.9 and 12.7 dB

73 de DG2YCB,
Uwe

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