Greetings all,
About the different SNR indications of WSPR-2 and -15 :
The question is how WSPR estimates the "noise" vale .. possibly
using the 'lower quartile' method described by G4JNT once upon a
time, i.e. sorting the FFT frequency bins from a certain
frequency range (which.. ?) by amplitude and taking the
<N/4-th> bin, corrected by something, as an estimate for
the noise level ?
In that case, because I guess the frequency bins are only 1/8th
as wide in WSPR-15 than in WSPR-2, the indicated noise level may
depend a lot on the drift rate of all those 'nasty little QRM
spikes' (in the spectrum), and this may be different for each
and every receiver location.
Here are my decodes for DF6NM and G4JNT (maybe Markus wants to
compare)..
WSPR-15:
2245 -2 -1.3 0.475824 0 DF6NM JN59 27
2315
-20 -0.6 0.475810 0 G4JNT IO90 33
2330
-8 -1.3 0.475824 0 DF6NM JN59 27
2345
-17 -0.6 0.475810 0 G4JNT IO90 33
0015
-15 -0.9 0.475810 -1 G4JNT IO90 33
0030
-2 -1.3 0.475824 0 DF6NM JN59 27
0100
-17 -0.6 0.475810 0 G4JNT IO90 33
0130
-11 -0.6 0.475810 0 G4JNT IO90 33
0130
-6 -1.3 0.475824 0 DF6NM JN59 27
0230
-5 -1.3 0.475824 0 DF6NM JN59 27
0245
-20 -0.6 0.475810 0 G4JNT IO90 33
0330
-7 -1.3 0.475824 0 DF6NM JN59 27
0345
-31 -0.9 0.475810 -1 G4JNT IO90 33
(btw
interesting to see G4JNT dropping so low at 03:45, guess that
one would possibly NOT have been decoded in WSPR-2)
DF6NM
in WSPR-2:
2328 -11 -1.5 0.475791 0 DF6NM JN59 27
2346 -11 -1.7 0.475791 0 DF6NM JN59 27
0028 -7 -1.7 0.475791 0 DF6NM JN59 27
0046 0 -1.5 0.475791 0 DF6NM JN59 27
0128 1
-1.5 0.475791 0 DF6NM JN59 27
0228
-3 -1.5 0.475791 0 DF6NM JN59 27
0246 -2 -1.7 0.475791 0 DF6NM JN59 27
0328 -5 -1.4 0.475791 0 DF6NM JN59 27
0346
-12 -1.5 0.475792 0 DF6NM JN59 27
From
the last transmission (03:30 to 03:45 in WSPR-15): -7 dB
Average between the adjacent WSPR-2 transmissions: -8.5 dB
(->
very similar results as from SM2DJK and DG3LV.... -15 shows
1.5 dB "better")
73,
Wolf DL4YHF
(receiver several hundred meters away from houses, but
mains-fed -> QRM)
Am 31.05.2015 02:07, schrieb Markus Vester:
Yeah maybe. But at the moment
I'd rather keep things as simple as possible, and I anyway
wouldn't expect a sharp optimum regarding speed.
The idea is to compare the SNR
of the slow sequence with the average of the two surrounding
fast sequences, received by the same monitor. If the dB
results were the same, we could probably exploit the full 9
dB advantage due to the lower threshold (-38 vs -29 dB),
otherwise we'd have to subtract the dB difference.
Results from first round:
2015-05-30 23:46 DF6NM
0.475791 -11 0 JN59nj 0.5 DL4YHF JO42fd 359
330
2015-05-30 23:30 DF6NM 0.475824 -8 0 JN59nj
0.5 DL4YHF JO42fd 359 330
2015-05-30 23:28 DF6NM 0.475791 -11 0 JN59nj
0.5 DL4YHF JO42fd 359 330
=>
WSPR-15 SNR happened to be 3 dB better!
2015-05-30 23:46 DF6NM
0.475790 -15 0 JN59nj 0.5 SM2DJK KP03au 1694
15
2015-05-30 23:30 DF6NM 0.475823 -13 0 JN59nj
0.5 SM2DJK KP03au 1694 15
2015-05-30 23:28 DF6NM
0.475790 -14 0 JN59nj 0.5 SM2DJK KP03au 1694
15
=>
WSPR-15 shows 1.5 dB better.
2015-05-30 23:46 DF6NM 0.475792 +1 0
JN59nj 0.5 DG3LV JO53gv 502 356
2015-05-30 23:30 DF6NM 0.475824 -2 0
JN59nj 0.5 DG3LV JO53gv 502 356
2015-05-30 23:28 DF6NM 0.475792 -8 0
JN59nj 0.5 DG3LV JO53gv 502 356
=> WSPR-15 shows 1.5
dB better.
This is an unexpected result, implying that the
advantage of WSPR-15 would be more than 9 dB, instead of
less. But on the other hand the dB values may not be
telling the whole story, because the threshold for a
fading signal might still be higher than -38 dB.
All the best,
Markus (DF6NM)
Sent: Sunday, May 31, 2015 1:33 AM
Subject: Re: LF: Dual-speed WSPR
Markus,
What about the old slow-WSPR by DF6NM? It could be useful to try
WSPR-4 for experiments. There is not just 2 and 15. And WSPR-120
on VLF... No problem!
73, Stefan
Am 31.05.2015 01:28, schrieb Markus Vester:
To allow SNR comparisons at
different speeds, I will transmit a mixed-mode beacon
tonight. It will consist of two WSPR-2 sequences, before
and after a WSPR-15 sequence on each odd half hour:
hh:28 - hh:30: WSPR-2
475.790 kHz
hh:30 - hh:45: WSPR-15 475.823 kHz
hh:46 - hh:48: WSPR-2
475.790 kHz
Transmitter power is currently 25 watts into
an antenna with 2% efficiency. Am listening to both
modes at all other times.
All the best,
Markus (DF6NM)
