Hi Fred,
Maybe American Samoa and Jarvis are not ideal locations, in terms of
signal propagation, for my station, which is located in Rio de Janeiro,
Brazil.
I have not been able to heard both of the two DX expeditions and this is
one of the reasons that pushed me to follow the Gary's analysis about SF
versus previous FH.
Really I need to wait for next SF expedition, in order to have a better
vision of the performances of the new mode, before to make any statements.
In any case I trust and agree with your and the others comments on this
matter.
73, Marco PY1ZRJ
Il 24/08/24 20:47, Frederick Kepner ha scritto:
Marco,
You stated that " FT8 is (should be) seen as a low power high S/N
efficient transmission mode". If you were struggling to hear N5J
during the DXpedition, you certainly would have difficulty hearing
them if they were running low power FT8. The RIBs (Radio in a Box)
they used were running amplifiers, I believe 500watts on FT8.
Super Fox was/is an improvement over the traditional Fox/Hound. It
permits more stations to be worked by the fox without sacrificing
output power. I watched them work both Super Fox and Fox/Hound and it
was obvious to me that the signals I received were generally
stronger/louder when he was running Super Fox.
Comparing this DXpediton to other DXpeditions probably isn't fair.
The N5J group was given antenna limitations by the US Fish and
Wildlife Service, who controls access to the island. You may have
been able to hear them with more success if they were permitted to run
directional antennas pointed your direction.
Personally, I was blown away at the signal strength improvement when
Superfox was tested on American Samoa and again when it was utilized
on Jarvis.
73
Fred
K3FRK
On Sat, Aug 24, 2024 at 5:51 PM Marco Calistri via wsjt-devel
<wsjt-devel@lists.sourceforge.net> wrote:
I'm with your thought, Gary and if you and others permit me, I
would add that FT8 is (should be) seen as a low power high S/N
efficient transmission mode, then it is particularly useful and
welcomed for modest ham-radio stations like mine.
If now, to work a DX Expedition which is using SFox we would need
a multi-elements Yagi beam and at least 500 Watts of RF power,
this beautiful "FT8 concept" disappear!
---
*73 de Marco, PY1ZRJ (former IK5BCU)*
**
Il 24/08/24 18:12, Gary via wsjt-devel ha scritto:
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 <wsjt-devel@lists.sourceforge.net>
<mailto:wsjt-devel@lists.sourceforge.net> 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
<wsjt-devel@lists.sourceforge.net>
<mailto:wsjt-devel@lists.sourceforge.net> wrote:
The bottom line is SF mode IS self defeating when/where
conditions are marginal AND they are always marginal
somewhere in the world
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