Hi
Stefan
Thank you for the detailed explanation. I prefer to
understand the process rather than getting a working .usr
So, excuse me again for dumming again J
All understood about the length and relation to FFT
windows time (length) in SL. Width was un unknown parameter for me
And I’m afraid the problem is about the width:
>>
Choose the FFT width and length to suit your settings.
The width is maybe 10 * 1/(symbol length) or more
Lets say 1Hz minimum for a 10 sec symbol leght, right ?
So, in the FFT configuration window the only way to get
>1Hz(1.3Hz) for “Width of one FFT-bin” is to reduce decimation to 1
and then set FFT length to 32768 to get some “FFT window
time (length)”. But then, the indows time is just 743ms
which will not cover the length of the message at all
I’m stucked here. Can’t get >width with 30 minutes FFT
lenghts. I’m using 44.100Hz sample rate
L
The FFT input type is “Complex ith internal frequency
shift”. But even using “Real FFT starting at 0Hz” doesn’t improve much
Decimation at 1536 and FFT length 65535 produces “Width
of one FFT” at 438uHz and FFT windows time 38 min. So this time
good length but small width
What I’m doing wrong ?
73 de Luis
EA5DOM
Hi Luis,
Am 10.09.2018 17:47, schrieb VIGILANT Luis Fernández:
The fact of getting windows timestamped files which
really start at a
different time and no aparent indication of when they end
….. doesn´t help at all
Well, the FFT settings must be so that you cover
enough width (in Hz) and length (in seconds). The necessary width
depends on your symbol length. The length is mentioned in the FFT
settings register card (FFT window time). Choose a rectangular window
for EbNaut decodes.
Convert the txt files into wav using Markus tools. Load the wav file in
the EbNaut decoder and press RUN. Then you will see the start time of
the file. The end is start time + length. Simple, isn't it? :-)
A new txt file is generated in the interval of the scroll time
(Spectrum (1) ) register card. Usually 30 minutes is fine, or even 1
hour on VLF. Then you get a file each 30 minutes. If the FFT length is
longer than 30 minutes. Your FFT length should be 30 minutes longer
than the transmission length, just to avoid an incomplete set of data
in a txt file.
Choose the FFT width and length to suit your settings. The width is
maybe 10 * 1/(symbol length) or more.
Is there any way of “fast” EbNaut when signals are strong
?
I think there are no limits, you can run 0.1
second symbol length. But usually it is used for weak signals and
stable paths.
I really don’t know what to test next.
Send me your .usr file and the EbNaut settings
you want to try.
73, Stefan
May be to run ebnaut_tx in test mode, which just changes
the phase every symbol length
And then, analyze the recorded file with a different tool
to determine if this phase changes are there ? Can this be easily done ?
73 de Luis
EA5DOM
PS: Congratulations for your amazing test with the guard
rails. And yes, this is much much harder than EME !
J
Hello Luis,
Another hint: Try to use 4K19A and a shorter message, like EA5 or so.
Use long symbols, like 10 seconds or longer. Then, timing is less
critical and you may get a decode and can tune to the best Eb/N0 and
find out what the timing offset it. It would guess it is a timing
problem.
73 Stefan
Am 07.09.2018 13:36, schrieb VIGILANT Luis Fernández:
Hi
Domenico
Sorry, I’m not transmitting this weekend. Very stormy
weather here, so the wires are down
I will notice in the reflector any transmission in
advance. But first want to confirm that all is working ok
So that was the goal of yesterday test
Yes, the XOR is AFTER the 1/10 divider, and working at
the final frequency 137485 Hz
Your auto-decoder is a great tool. EbNaut is quite tricky
for average use and needs a lot of details to care about
Of course the reward is great when you get decodes with
miserable signal levels. There is never free lunch ! ;-)
73 de Luis
EA5DOM
De:
[email protected]
[mailto:[email protected]]
En nombre de Domenico IZ7SLZ
Enviado el: viernes, 07 de septiembre de 2018 13:18
Para: [email protected]
Asunto: Re: LF: EbNaut transmission test in LF
BTW QRM is large here in the morning time
(urban location). I will try to catch your signal later in the night.
At least the decoder
is detecting the carrier but may be there is no proper phase modulation
or probably other failures
What I’m doing wrong ?
Can anybody decode the message from the file ?
I also suspect some issues on modulator
circuit. Of course the XOR gate is following the /10 divider, is it?
Hi LF EbNauters
I have been building a
disciplined Rx for LF, based in a GPS LO at 120KHz and a NE602
downconverter to 17KHz
Then feeding the signal
to the soundcard, also disciplined with 1pps from the same GPS
At Tx side a GPS LO at
1374850 Hz divided by 10 provides 0.1Hz steps at LF. Then an XOR gate
is used for
EbNaut modulation from
the DTR of a COM port under Windows. The PA is just a mosfet driver
(mic4452 AT 12v)
Just about 100mW to
antenna but good enough to get a 20dB S/N in my Rx 7Km away
Stability looks pretty
good and also phase modulation as seen in SL spectrogram. Also
monitoring phase changes
with the SL plot
display window. So, yesterday I tried an EbNaut transmission with the
following setup
Coding: 8K19A
CRC 16
Symbol period: 1s
Characters: 6
Transmission time: 9.3 minutes
Transmitting at minute
00 and 30 every hour
I got the FFT files
from SL and converted them to WAV files. The configuration file (SR)
included the corrected sample rate
of the soundcard as
well as decimation , FFT length and center frequency
Attached is a WAV file
starting at 16:22 which should contain the transmission started at
16:30 untill about 16:40
The rawsym graphic
shows a clear peak centered in frequency, but I haven’t been able to
get a decode other than “******”
At least the decoder is
detecting the carrier but may be there is no proper phase modulation or
probably other failures
What I’m doing wrong ?
Can anybody decode the message from the file ?
BTW, I have used a list
length of 47274 and also 141823, but nill
L
73 de Luis
EA5DOM
