Hi Reino,
We could do simulations for the "High-latitude Moderate" (HM) channel,
of course, but have not done do. We do know that FT8 does not do very
well under such conditions (Doppler spread = 10 Hz, Differential delay 3
ms): see Figure 7 and Table 6 of our QEX paper on FT4 and FT8, here:
https://wsjt.sourceforge.io/FT4_FT8_QEX.pdf
Steve did simulations for a path fairly close to the HM parameters:
Doppler spread = 5 Hz, Differential delay 3 ms. Curves for these
results are included in the plot I've posted here:
https://wsjt.sourceforge.io/fig_superfox_ft8b.pdf
As you can see from the curves with triangle points, sensitivities for
SuperFox and FT8 are nearly the same (within about 1 dB) on this path.
We also know (Fig 7, QEX paper) that the FT8 curve for HM fails to
approach a decode probability of 1.0 at high SNRs.
-- 73, Joe, K1JT
On 9/7/2024 5:41 AM, Reino Talarmo via wsjt-devel wrote:
Joe,
Thank you about the excellent document. It does clarify
where we are at the fight against noise and signal
spreading.
I am interested to see also results for the
"High-latitude Moderate" propagation model for SF. FT8
have a lot of difficulties on that kind path as
presented in Figure 7 of The FT4 and FT8 Communication
Protocols. FT4 in that figure may give a hint. I assume
that a part of N5J QSO difficulties was the inferior
decoding of FT8 over the polar path not the SF signal.
There was sometimes also unintended FT8 QRM on the even
timeslots adding repeats from fox.
73, Reino OH3mA
-----Original Message-----
From: Joe Taylor via wsjt-devel <wsjt-
de...@lists.sourceforge.net>
Sent: Friday, September 6, 2024 10:54 PM
To: wsjt-devel@lists.sourceforge.net
Cc: Joe Taylor <j...@princeton.edu>
Subject: [wsjt-devel] SuperFox and FT8: Weak-Signal
Performance
Hi all,
WSJT-related lists have recently seen a lot of
discussion
about FT8 and SuperFox decoding thresholds. Some of
it has been incorrect or misleading.
I have posted a short document comparing measured
sensitivities of SuperFox and FT8 (including multi-
streaming) here:
https://wsjt.sourceforge.io/SuperFox_Performance.pdf .
-- 73, Joe, K1JT
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