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Re: LF: Phase shifts on 137.777 kHz

To: [email protected]
Subject: Re: LF: Phase shifts on 137.777 kHz
From: Markus Vester <[email protected]>
Date: Sat, 21 Nov 2015 16:57:23 -0500
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Hi Joe,
 
phase shift is working - two peaks at +- 10 mHz, as expected. Updating spectrogram:
 
Yes the start of the message and the bit timing need to be referenced to UT, and we have to provide this information to the decoder. You can make a choice on the symbol duration, based on available SNR, length of message etc.
 
Currently each of the two carriers is ~ 24 dB SNR in 1mHz here. A straight carrier would be 4 dB stronger, giving -2 dB SNR in 1 Hz. This means that you could theoretically achieve a 0 dB Eb/N0 decode here if you sent 0.63 info bits per second (6 characters per minute), using ~ 0.2 s symbols. But I would probably prefer to start slower, with something like 1 or 2 second symbols to have some margin for QSB and more distant receivers.
 
Best 73,
Markus
 
 
 
 
 
 

 

-----Ursprüngliche Mitteilung-----
Von: jcraig <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Sa, 21 Nov 2015 8:47 pm
Betreff: LF: Phase shifts on 137.777 kHz


Dear Group, 

Hopefully I've finally got it right... Inversions every
50 seconds a dozen times then 100s of silence.

Hopefully QRV on EbNaut in the near future. I have a long
list of 1s and 0's loaded and ready to send. Doing:
./ebnaut -dt -N13 -p 4K19A < ebcode.txt
gives back the message even if I try hard to mess up ebcode.txt

If I scan ebcode.txt & use phase=bit*pi, how long should my
bits be keyed? Is synchronisation against UT critical?

Please excuse my earlier failed efforts & silly questions.

73
Joe VO1NA




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