Hi Scott,
Linux and Mac systems nearly all have accurate time synchronization
without any extra user setup. Obviously if no suitable Internet
connection nor GPS receiver is available then the same issues apply.
73
Bill
G4WJS.
On 03/05/2019 22:05, V. Scott Moore via wsjt-devel wrote:
Windows only or all platforms?
Scott W1ssn
Sent from my iPhone
On May 3, 2019, at 4:58 PM, Bill Somerville <[email protected]
<mailto:[email protected]>> wrote:
On 03/05/2019 21:24, Reino Talarmo wrote:
Hi,
Thanks for an excellent piece of communication protocol both FT8 and
FT4. It would be interesting to see how big guns start to use FT4
instead of RTTY. For strong signals RTTY is a bit faster than FT8,
but most of the users are not big guns! The bandwidth saving in FT4
is a really big issue, so there will be many more QSOs/min/kHz.
I checked how much timing difference is allowed for a successful
decode. It seems that in 23000 successful decodes timing difference
is in range -0.5 s to 0.6 s. In FT8 the range is -2.6 s to 2.5 s and
99% of successful decodes are within +/-2 s compared to my timing. I
have no idea how much signal strength affects to the result, but for
sure in FT4 any practical signal strength increase does not help to
extend the range outside the +/- 0.5 s. There are many signals that
fall out of that range. So we could recommend clock accuracy +/-
0.25 s or better for FT4.
73, Reino oh3ma
Hi Reino,
your conclusions are all correct. We are currently fine tuning the
FT4 transmission start time so that the decoder gets a reasonably
even chance of decoding signals across the allowable DT tolerance of
± 0.5 S without losing sensitivity. We can't quite make it perfect
across that range whilst still allowing the user reasonable thinking
time before the next transmission period. FT4 has a shorter
transmission time, shorter dead time between periods, and shorter
periods than FT8 so it should not be surprising that clock accuracy
requirements are stricter as well. This really only matters for MS
Windows users who have not bothered to install a third-party NTP
service, have no suitable Internet connection, or GPS signal. For
those that rely on manual time setting or think Windows can do the
job well enough, now is the time to think again.
73
Bill
G4WJS.
_______________________________________________
wsjt-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/wsjt-devel
