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
