LF: VO1NA - IZ7SLZ

[Markus Vester <markusvester@aol.com>]

During the last few nights, Domenico recorded spectrum data files around 477.69 kHz and placed them in a public directory: https://www.dropbox.com/sh/zu0k37z95ft1xfw/AAAgwsWDdfHVxTByuT8CyY_2a?dl=0 .

During the early morning yesterday (Mar 3), conditions into central Europe seemed favourable. I downloaded several files and attempted to decode them. Despite the fact that no carrier trace was visible in Domenico's 0.48 mHz spectrogram  https://www.dropbox.com/s/fsjkfuhggozzv5w/grabber.jpg?dl=0 , the file centered on 1:40 UT produced a single good decode of VO1NA in South Italy (see attached screenshots).

So I happily pass the receive part of the MF EbNaut distance record on to IZ7SLZ. Warm congratulations to Joe and Domenico!

Best 73,
Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: Markus Vester <markusvester@aol.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Do, 3 Mrz 2016 1:12 pm
Betreff: Re: LF: MF: EbNaut

Hi Joe,

last night propagation between us was unusally stable and very strong until ~ 5 UT:
 https://dl.dropboxusercontent.com/u/26404526/opds8.png
The FFT bandwidth had been halved to increase the aquisition time for your longer transmissions.

"G. MARCONI"
VO1NA, 477700Hz, 4K19A, 10char, 752*2s

Wed/Thu 2016-03-02/03

start  car. sym. offs.
 UT    dB   dB   mHz
23:30 11.9  7.9   0
00:00 12.9  10.0 -1.5
00:30 16.1  13.6 -1.5
01:00 11.6  8.3  -1
01:30 16.9 14.2  -0.6
02:00 10.7  8.3  -0.6
02:30 17.9 14.4  -0.6
03:00 14.1 10.8  -0.6
03:30  5.7  4.4  -0.8
04:00  5.2  5.1  -0.8
04:30  3.6  4.0  -0.8

Compared to yesterday, I think the much larger SNR is mostly due to more stable phase rather than longer symbols. I found that still had to individually tweak the frequency offset in small steps, starting EbNaut several times and watching the decode quality after the first linear-phase trials, as well as the dots in the rawsyms phase plot. 

Generally on MF shorter much shorter symbols may be preferable. I believe that for such coherent and un-referenced signaling, there should be an optimum total message duration which is related to the inverse of the propagational Doppler spread. If that is typically 10 or 20 mHz, only a couple of minutes may be best.

Hope that Domenico may have been able to break our distance record. Using phonons instead of photons might be too much of a challenge though ;-)

Best 73,
Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: jcraig <jcraig@mun.ca>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mi, 2 Mrz 2016 11:43 pm
Betreff: Re: LF: MF: EbNaut

Hi Markus and thank-you for your patience and coaching. I was only there
to put your ideas into practice.

I feel bad for making Paul's record so short lived, but very grateful for
his software and guidance.

Well lets go for 2 seoond symbols tonight and hope that enough phonons
will reach Italy tonight.

73 and many thanks Markus and Paul
Joe

03030140_result_iz7slz.png
Description: PNG image

03030140_sym_iz7slz.png
Description: PNG image