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This phenomen,or rather bug,has been reported here
by several list members.
I have made the same observations.
Reducing the RX BW from e.g. 250Hz to something
below 100Hz results in
an increase of *reported* SNR of up to around
15dB!
I've done some tests with a friend 20km away on 10m
and we've found out that the *real* SNR
is not improved a bit or in other words an extreme
weak wspr signal which was just below
the decoding threshold in 250Hz BW coudn't be
decoded with 20Hz BW either.
73
Clemens
DL4RAJ
----- Original Message -----
Sent: Wednesday, January 27, 2010 9:44
PM
Subject: Re: LF: RE: WSPR Reports
All the critical filtering is done in the software, and results in a
1.46Hz noise bandwidth - which is what the software measures and reports
upon.
Your observation that a narrower IF bandwidth is interesting.
Its most likely based on the fact that typical signals are corrupted by pulsed
non-gaussian noise which upsets the frequency bin detection process, and
upsets sync recovery.
Andy www.g4jnt.comThis email has been
scanned for damaging side-effects by the health and safety police, is
guaranteed to contain no substances hazardous to health, but may contribute to
dissolving the nether and polar regions 2010/1/27 Rik Strobbe <[email protected]>
Andy,
maybe the "magic" lies in a
narrow filter (either IF or audio).
If I switch from a 2.5kHz (SSB) filter
to a 270 Hz filter I also get a significant increase in SNR values
reported by WSPR.
Unfortunaely it hardly affects the
decoding level (minimal SNR needed to get a positive decode), that rises by
almost the same amount.
73, Rik ON7YD -
OR7T
Has F6CNI managed some sort of magic noise reduction system, or is it a
just a case of being in a very quiet location...
These are pretty impressive S/N values
| 2010-01-27 20:14 |
G4JNT |
0.503875 |
+13 |
0 |
IO90iv |
+23 |
0.200 |
F6CNI |
JN19qb |
391 |
243 |
| 2010-01-27 20:08 |
G4JNT |
0.503875 |
+10 |
0 |
IO90iv |
+23 |
0.200 |
F6CNI |
JN19qb |
391 |
243 |
| 2010-01-27 20:02 |
PA0A |
0.503900 |
+15 |
0 |
JO33de |
+37 |
5.012 |
F6CNI |
JN19qb |
502 |
312 |
| 2010-01-27 20:00 |
G4JNT |
0.503875 |
+14 |
0 |
IO90iv |
+23 |
0.200 |
F6CNI |
JN19qb |
391 |
243 |
| 2010-01-27 19:54 |
G7NKS |
0.503920 |
-5 |
0 |
IO92ub |
+20 |
0.100 |
F6CNI |
JN19qb |
422 |
262 |
| 2010-01-27 19:54 |
G4JNT |
0.503875 |
+14 |
0 |
IO90iv |
+23 |
0.200 |
F6CNI |
JN19qb |
391 |
243 |
| 2010-01-27 19:44 |
G4JNT |
0.503875 |
+10 |
0 |
IO90iv |
+23 |
0.200 |
F6CNI |
JN19qb |
391 |
243 |
| 2010-01-27 19:40 |
PA0A |
0.503900 |
+15 |
0 |
JO33de |
+37 |
5.012 |
F6CNI |
JN19qb |
502 |
312 |
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