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Re: [wsjt-devel] SuperFox vs Fox
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From: Jim S. <ji...@gm...> - 2024-08-24 22:02:32
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You are comparing apples to oranges. A -17 FH signal is not the same as a -17 SF signal. Per the FH docs "for N Slots = 1, 2, 3, 4, and 5 the average power per signal will be down from P0 by about 0, 6, 9.5, 12, and 14 dB, respectively". So you have a 9.5 dB hit per stream for three streams. Or to put it another way, a single stream would be 9.5 dB stronger. SF is a single stream transmission so it is at 0 dB all the time. This is covered in greater detail in the developer docs but there is a net "gain" for SF over a certain number of FH streams. I have what you describe as a small station. Again, I have N5J contacts in the log that I would not have if they were running multi-stream FH. It was six days in before I heard and worked N5J on 10 and 12 SF but patience and good software tools got me to the right spots (no pun intended) at the right time. 73 -Jim NU0C On Sat, 24 Aug 2024 17:12:25 -0400 Gary via wsjt-devel <wsj...@li...> wrote: > Exactly. The reduced overall sensitivity compared to 3 stream regular > F/H was at play in my case. On 3 streams, they decoded on regular F/H > at -17. Weak, but well within the -24db decoder limit. A -17db signal > on Super F/H is outside of that decoder's limit of -16. It makes a > difference for those of us forced to use marginal stations. Also, the > 1500hz bandwidth makes it more prone to QRM, as I see it. > > I hope that DXPeditions from now on will not be using S/FH exclusively, > or myself and a lot of other small stations are going to be left out, > unless the SFX runs some power. Like 40-100w at least. I heard that > N5J was only running 10w. That could have been a big part of the > problem, if true. > > 73 de Gary - W9BS > > On 8/24/2024 4:50 PM, Jim Shorney via wsjt-devel wrote: > > It is a matter of deciBels as has been documented. Each time a stream is added in multi-stream there is a multi-dB power hit on all streams. This is what SF avoids but TANSTAAFL. You do lose some sensitivity but at that point you would probably not be hearing multi-stream FH either. It seems like you were a victim of propagation. If you were copying three streams of FH you probably could have copied SF under the same conditions. Just a guess as there are multiple factors in play. I was decoding SF more reliably than anything over 2 FH streams. It is rare that I am able to copy three or more FH streams when prop is poor. Signals have to be very good. That is not the fault of the software, it is the limitations imposed by my antenna system and local noise floor vs. propagation conditions. > > > > 73 > > > > -Jim > > NU0C > > > > On Sat, 24 Aug 2024 12:10:02 -0400 > > Gary via wsjt-devel <wsj...@li...> wrote: > > > >> Perhaps it is a problem when running 5 streams. But my experience was > >> just the opposite. I could never hear them on SFox on any band. > >> Admittedly, I run a low profile station with an attic antennas. From > >> this perspective, SFox was a huge disappointment. It wasn't until they > >> switched to regular fox near the end of their deployment that I was able > >> to finally work them on 17 and 30. They were running 3 streams at the > >> time. Never decoded them once on Superfox on any band, after > >> frustratingly listening for them all week. > >> > >> 73 de Gary - W9BS > >> > >> On 8/24/2024 11:51 AM, Jim Shorney via wsjt-devel wrote: > >>> But the same can be said of multi-stream F/H. I can say with certainty that I have Super contacts in the log with N5J that I would not have if they had been using multi-stream. > >>> > >>> On Sat, 24 Aug 2024 13:48:02 +0000 (UTC) > >>> Greg Chartrand via wsjt-devel <wsj...@li...> wrote: > >>> > >>>> The bottom line is SF mode IS self defeating when/where conditions are marginal AND they are always marginal somewhere in the world > >> > >> _______________________________________________ > >> wsjt-devel mailing list > >> wsj...@li... > >> https://lists.sourceforge.net/lists/listinfo/wsjt-devel > > > > > > > _______________________________________________ > wsjt-devel mailing list > wsj...@li... > https://lists.sourceforge.net/lists/listinfo/wsjt-devel -- 73 -Jim NU0C |
