Hi Stefan, EbNaut
Not sure if the phase is exactly shifted 180º but should be. I pass the 137KHz signal trought an XOR gate, the other input of the XOR
is controlled by the DTR level of a COM port under windows. I use Paul’s “ebnaut-tx.exe” for windows
http://abelian.org/ebnaut/win32/ebnaut-tx.exe
Yes. The carrier is transmitted permanently and then there is phase modulation for the transmission periods
Not using SpecLab for Tx. Just for Rx
The message is my callsign. Six characters. EA5DOM
Thank you for the tips. Sure there are other message configurations which should be more apropiate for a first test
Unfortunately this weekend we have a lot of storms and thunders. So can not keep transmitting, but may be a local signal
should work close to the Rx
73 de Luis
EA5DOM
Hi Luis,
Are you sure that the phase shift is 180 deg? At 180 deg there should be no peak in the red spectrum (Markus' tool show_rawsyms3b). Are you transmitting the carrier permanently and just do the keying for those 9.3 minutes? Then maybe there is just a timing
problem.
Do you generate the RS232 keying with SpecLab? If so, do you consider SpecLab's internal time offset of 0.3 seconds + 4/samplerate? Here it is 0.812 seconds, which is a very significant part of the symbol length and thus most important to consider. However
i'm not sure if this also applies when using the serial interface...
Can you tell me the message? It is easier to find the reason when already knowing the message.
73, Stefan
Am 07.09.2018 11:28, schrieb VIGILANT Luis Fernández:
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
