Your critiques of my signals are very thorough and masterful.  I am
most grateful.  There is a concensus amongst you, Domenico and Stefan
that I've gone off frequency again, at times more than 1 mHz!
Hopefully this will be corrected soon. I'll post your nice plots
on the web if you don't mind.

In the mean time, I ran Paul's ebbaut.c on the MUN unix box and
an old Model B raspi. It compiled flawlessly.  I had to put in
arguments for -S and -r which I chose at random, my callsign and
pussycat's name and was rewarded with a long list of 0's and 1's.

So if I send a long carrier with a phase inversion every time a 1
is encountered, it will be a valid ebnaut transmission? What is
the duration of the elements and what arguments should I pass to
ebnaut.c?  Also, would a transformer + DPDT relay work?  A ring
mixer might not take kindly to a 12V squarewave.

Please excuse my naivety!  Also, XYL is wondering why you want the
other details of the cat.  She was my ground crew today while I was
atop the tower so I must be diplomatic!

MNI TNX
Joe VO1NA

On Wed, 11 Nov 2015, Markus Vester wrote:

Joe,
 
more of the same from last night, this time with frequency and level plots. 
Again we see some frequency variation of similar size as yesterday. It is not 
clear how much of that is due to propagation, I only think that 
the rise near the end is due to Doppler from the descent of the ionosphere 
at sunrise. Russian Loran lines on 137475 and 137482.5 seemed to have less 
overnight variation (~ 0.1 mHz), but then of course the intra-European path 
from Slonim is very different from yours. 
 
Regarding EbNaut carrier analysis: for some reason (lack of coffee?), I only 
saw Domenico's earlier mail after I had sent mine, so please excuse me for 
basically having described the same procedure again. Anyway it's good that 
we both arrived at the same conclusion: If Joe started sending EbNaut PSK 
with his oscillator as it is now, we would very likely be able to decode it 
here. 
 
Joe so all you need now is a diode ring-mixer for PSK modulation and Paul's 
ebnaut-tx program. Symbol timing will be derived from the PC clock, so 
with NTP available there's no need to involve GPS at all. If Paul brought his 
LF receiver back to life, he could probably copy you even if you reduced TX 
power to 0.1 Deccas.
 
How many cats do you have? We want to know names, colours, sex and age for all 
of them ;-)
 
All the best,
Markus (DF6NM)
 
 
PS. SpecLab question: Wolf is there a way to extract peak frequencies from past 
spectrogram lines (semi-)automatically, without having to manually move and 
read the mouse cursor over each point, e.g. something like a peak_f(f1,f2, 
time) interpreter function?

 
-----Ursprüngliche Mitteilung-----
Von: Markus Vester <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Mi, 11 Nov 2015 1:24 am
Betreff: LF: VO1NA frequency
       Hi Joe,
 
the attached plot shows the  frequency stability of your opds trace received last  
night http://df6nm.bplaced.net/LF/opds32_151110_0736.png .  Each data point is the interpolated peak of a  
single 438 uHz FFT (i.e. 38 minute window). The average frequency seems to be  0.7 mHz below nominal, and 
there are small temporal variations up  to 0.5 mHz in either direction. Though some of that is  
probably attributable to noise and propagation, I believe that there  is also a bit of inherent instability 
in the frequency  source. Actually a few parts per billion is quite good for a free  running OCXO 
(assuming the "D" stands for  "double oven" and not "discipled"), and that the 
calibration was done over a 10  MHz HF link.
 
Is this good enough for EbNaut? During the  experiments with IZ7SLZ we found 
that for full sensitivity the phase variation  over the EbNaut sequence 
duration should not be much more than 90°. Thus  for a half-hour message the 
frequency should be ideally constant and known to  about 0.14 mHz. If there is 
more variation we often can still  get decodes, but we will have to find 
the best frequency offset by trial  and error, which can be cumbersome if the 
signal is weak.
 
I also fed opds data files from your Sat/Sun  transmissions to the EbNaut decoder. The 
idea was to see if your Opera  transmissions would actually produce the 
all-asterisk decode which is  expected for a non-PSK-keyed straight carrier, and to 
observe the symbol phase  evolution over the 38 minute duration. Starting midnight UT, 
one decode was attempted every 30 minutes,  using a setting for 464 raw symbols (4 
characters) and 5 seconds per  symbol. A frequency offset of -0.6 mHz was selected to 
obtain  flat phase during the first decodes, and that offset was kept for  all later 
attempts. Despite the Opera gaps  which degrade or drop half of the available 
symbols, 12 out of 13  decode attempts produced the  correct "****" 
message, e.g. http://df6nm.bplaced.net/LF/r0317.png  . However at times the frequency 
drift was quite visible on the phase  plot, e.g. in 
http://df6nm.bplaced.net/LF/s0317.png (flat  phase around 3:17) versus 
http://df6nm.bplaced.net/LF/s0347.png (upward  phase slope around 3:47). 
 
Scaling down to VLF, deviations from the same  oscillator will be 16x smaller 
(~30 uHz at 8.3 kHz). This will be probably good  enough even for narrow FFT 
bins, corresponding to several hours coherent  carrier integration or slow 
EbNaut decodes.
 
All the best,
Markus (DF6NM)


 From: [email protected]
Sent: Saturday, November 07, 2015 3:45 PM
To: [email protected]
Subject: Re: LF: VO1NA opds-32




LF Group,

Again, thanks to SV8RV DF2JP PA7EY and DF6NM for  the reports.

In my last post I reported the drift was constrained to  within 1 Hz.
This should be 1 mHz.  Thanks Markus for your assurances  that this
should be adequate for EbNaut which I hope to use to send send our
cat's name on LF.  The little curls appear often on the QRSS traces  on
your high res spectra.  Doppler variations were removed from the 10  MHz
WWV signals with harmonic regression when the DOCXO was calibrated
so  this effect is seen on LF but not as strongly.

After  reading about  EbNaut on Paul Nicholson's pages it seems I have
much catching up  ahead.  Fasinating stuff!

Can the EbNaut phase inversions be done  without an absolute time
reference?  I'm cheap and lazy so hoping GPS  will not be needed.

The Opera will be doing an encore tonight and if the  wind stays low
a tower climbing expedition is planned for the  afternoon.

73
Joe VO1NA


On Sat, 7 Nov 2015, Markus Vester  wrote:

> Hi Joe, LF,
>
> during the last couple of nights,  opds detected all of your transmissions 
between about 22  and 7:30  UT.
>
> Attached is a zoomed 40 mHz section from my opds-32  spectrogram, showing 
your central coherent carrier which contains half of the  transmitted average 
power. It seems to be about 0.5 mHz below 137477 Hz  (possibly due to a calibration 
error in my receiver). The 2.7 mHz spaced  sidelines during the early part (bottom) 
were caused by 6-minute-periodic  interruptions from my own MF WSPR transmissions. 
However the little curls near  the carrier can presumably be attributed to 
Doppler-shifted multipath  components. The carrier was still weakly visible for 
another hour after the last  detection.
>
> Comparing the looks of the carrier to earlier IZ7SLZ  transmissions, the 
stability of the signal and the path seems quite sufficient  for half-hour EbNaut 
PSK transmissions. Unfortunately I missed the opportunity  to save the raw data and 
analyze phase evolution using the EbNaut decoder itself  - will try that next time.
>
> All the best,
> Markus  (DF6NM)
>
>
>
>
> From: [email protected]
> Sent: Saturday, November  07, 2015 12:03 AM
> To: [email protected]
>  Subject: Re: LF: last night opera opds detection in  km07ks
>
>
> LF Group,
>
>
> I am grateful  to Joe DF2JP for his captures QRSS and Opera
> Dionysious SV8RV for his OP  decodes to Domenico IZ7SLZ
> for his OPDS decodes, and thanks to DF6NM for  opds!
>
> I do not know if my DOCXO is stable enough for  EbNaut.
> It was set a couple of years ago and has not drifted more  than
> 1 Hz since then.  It seems the phase decoherence has  stopped
> haunting me.
>
> I am hoping to replace the halyard  for the other 100m wire soon.
>
> OP32 again tonight as send this  email.
>
> 73
> Joe
>
>