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LF: ebnaut results depend on sample rate

To: [email protected]
Subject: LF: ebnaut results depend on sample rate
From: Jacek Lipkowski <[email protected]>
Date: Fri, 12 Apr 2019 10:31:48 +0200 (CEST)
Reply-to: [email protected]
Sender: [email protected]
User-agent: Alpine 2.11 (DEB 23 2013-08-11)
For some reason the results i get from ebnaut are different depending on signal bandwidth. For Stefan's latest 2970.1Hz transmission it is better to use 10Hz sample rate than 240Hz:
10Hz:

[email protected]:/stuff2/sq5bpf/vlf_stefan2$ vtblank -v  -d0.0007 -a22 -t 70 < 
pliktmp7 |  vtmult -f 2970.1 | vtresample -r 240 |    vtresample -r 10 |vtraw -oa  
| ebnaut  -dp16K21A -r10 -c2 -v -k16 -S6 -N7  -PS -L 50000

vtblank: selected channel: 1 = -:1
vtblank: channels: 1, sample_rate: 48000
vtblank: hfactor: 0.000e+00
vtblank: afactor: 22.000
initial reference phase 88.1 amplitude 8.289e-04
phase   0    0    0    0    0
vtblank: end of input
vtblank: dropsum 0 50041841, nfp 359999999
vtblank: dropfactor 0 1.390e-01
phase   1  180  180  180  180
found rank 6348 ber 4.2147e-01 Eb/N0 -2.0 M -2.316530794e-02 ph 1 180,180,180,180 [DK7FC/P]
carrier phase: -10.7 deg
carrier Eb/N0: -0.3 dB
carrier Es/N0: -15.26 dB
carrier S/N: 15.70 dB in 133.5 uHz, -23.04 dB in 1Hz, -57.02 dB in 2.5kHz
elapsed 98
[... and no more decodes ]

240Hz:

[email protected]:/stuff2/sq5bpf/vlf_stefan2$ vtblank -v  -d0.0007 -a22 -t 70 < 
pliktmp7 |  vtmult -f 2970.1 | vtresample -r 240  |vtraw -oa  | ebnaut  -dp16K21A 
-r240 -c2 -v -k16 -S6 -N7  -PS -L 50000

vtblank: selected channel: 1 = -:1
vtblank: channels: 1, sample_rate: 48000
vtblank: hfactor: 0.000e+00
vtblank: afactor: 22.000
initial reference phase 89.2 amplitude 1.953e-02
phase   0    0    0    0    0
vtblank: end of input
vtblank: dropsum 0 50041841, nfp 359999999
vtblank: dropfactor 0 1.390e-01
found rank 43444 ber 4.0144e-01 Eb/N0 -0.0 M -5.377145410e-01 ph 0 0,0,0,0 [___!NL&]
carrier phase: 0.2 deg
carrier Eb/N0: -1.8 dB
carrier Es/N0: -16.72 dB
carrier S/N: 14.24 dB in 133.5 uHz, -24.51 dB in 1Hz, -58.48 dB in 2.5kHz
elapsed 96
phase   1  180  180  180  180
found rank 15563 ber 4.2067e-01 Eb/N0 -1.9 M -5.445608497e-01 ph 1 180,180,180,180 [DK7FC/P]
carrier phase: -11.8 deg
carrier Eb/N0: -1.5 dB
carrier Es/N0: -16.43 dB
carrier S/N: 14.54 dB in 133.5 uHz, -24.21 dB in 1Hz, -58.19 dB in 2.5kHz
elapsed 102
[...]
phase  17  180  180  150  150
found rank 16679 ber 4.3029e-01 Eb/N0 -3.1 M -5.484929085e-01 ph 17 180,180,150,150 [DK7FC/P]
carrier phase: 3.7 deg
carrier Eb/N0: -1.6 dB
carrier Es/N0: -16.53 dB
carrier S/N: 14.43 dB in 133.5 uHz, -24.31 dB in 1Hz, -58.29 dB in 2.5kHz
elapsed 201



With a couple of previous transmissions the result was better with 240Hz than with 10Hz. Not much of a difference, but this is the reason i've always used 240Hz.
Paul, any idea why there is a difference, and how to determine the best
sample rate?
VY 73

Jacek / SQ5BPF


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