thanks to Markus and Stefan for the comments and to Rob for putting on air a very good signal.
I was also surprised to see the decode achieved by the auto-decoder without any time and frequency offset !
Propagation conditions are becoming better, but noise here is still high.
I tried a deep investigation: no further decode, but with an offset of -0.0001 Hz and +0.005s (ooops !) i have improved the 2018-09-30_03:00 UT decode:
initial reference phase -62.3 amplitude 2.049e-01
phase 0 0 0 0 0
carrier phase: -6.9 deg
carrier Eb/N0: 0.5 dB
carrier Es/N0: -10.10 dB
carrier S/N: 19.87 dB in 672.0 uHz, -11.86 dB in 1Hz, -45.84 dB in 2.5kHz
found rank 43 ber 3.4980e-01 Eb/N0 -0.6 M -7.389708042e+00 ph 0 0,0,0,0 [K3RWR_FM18QI_73]
Looking on the October 1st recordings, with these offsets, i got another decode at 02:30 UT:
initial reference phase -6.6 amplitude 2.356e-01
phase 0 0 0 0 0
carrier phase: -1.2 deg
carrier Eb/N0: 0.4 dB
carrier Es/N0: -10.23 dB
carrier S/N: 19.74 dB in 672.0 uHz, -11.99 dB in 1Hz, -45.97 dB in 2.5kHz
found rank 84 ber 3.6694e-01 Eb/N0 -1.7 M -7.504411221e+00 ph 0 0,0,0,0 [K3RWR_FM18QI_73]
Working conditions here, (vintage 😀) as usual:
- miniwhip (a modified ex-Navtex antenna from Furuno ; see attachment)
- receiver JRC NRD-92M with external 10 MHz reference signal steered by GPS
- a modest PC (Intel P4 CPU 3.50GHz x2) from scrap with Ubuntu 14.04LTS
- software vlfrx-tool from Paul Nicholson.
I have attached also the latest version of the bash './autoebnaut' i.e. the list of the commands that recall vlfrx-tool programs to start the decoder each 30 minutes.
Other linux programs are running in background:
- vtcard and vttime to manage and calibrate the audio card
- vtwrite to store audio coming from receiver
- gpsd and chrony to manage the nmea and 1pps from neo8 gps (connected at serial COM1) and adjusting the PC clock.