I was amazed to learn from Paul
Nicholson that he was able to decode the complete MFSK-37 QSO
between OK2BVG and myself...
73, Markus (DF6NM)
Sent: Friday, March 30, 2012 10:48 PM
Subject: Re: VLF, messages received 2012-03-25
> Would you mind us forwarding your notice to the LF
reflector?
Sure. any message from me, you can forward if you think it of
interest.
Yes I was surprised it decoded correctly at the first attempt.
Was thinking S/N would be too low and expected also to have to notch out
8970.022.
BNM and RO were reliable copy, but NB and especially TU were
lucky, with the 'winning' bin only 2.2 times the mean amplitude of the other 36
bins, there were plenty of chances to get the T and U wrong.
I used a
program written some months ago - when you were experimenting with simulations
of PSK and MFSK. I wrote it to test your error-rate predictions (with which it
agreed perfectly). I made a minor change from MFSK64 to MFSK37 and let it run
over the recorded signal (mixed to a loop alignment of 110 deg and the usual
sferic blanking recipe) and out came the message first time.
Well done
both stations, hope we see more MFSK.
--
Paul
Nicholson
--
Sent: Friday, March 30, 2012 10:12 PM
Subject: Re: VLF, messages received 2012-03-25
Paul,
wow, that's impressive! I would not have thought
that this is possible - at your distance you can decode the complete
message, including the "TU", which had drowned in the afternoon noise in
OK.
Would you mind us forwarding your notice to the LF
reflector?
Thanks very much!
Markus (DF6NM)
Sent: Friday, March 30, 2012 1:42 PM
Subject: VLF, messages received 2012-03-25
Lubos, Markus,
I
ran my recording from the 25th through an MFSK37 decoder program. It
produced the following output:-
(asnr = amplitude S/N
ratio)
vtcodec: 2012-03-25_07:30:00.000 rxed [N] asnr 2.87
vtcodec:
2012-03-25_08:00:00.000 rxed [B] asnr 2.63
vtcodec:
2012-03-25_09:00:00.000 rxed [B] asnr 3.84
vtcodec: 2012-03-25_09:30:00.000
rxed [N] asnr 3.68
vtcodec: 2012-03-25_10:00:00.000 rxed [M] asnr
4.46
vtcodec: 2012-03-25_11:00:00.000 rxed [R] asnr 4.51
vtcodec:
2012-03-25_11:30:00.000 rxed [O] asnr 4.30
vtcodec:
2012-03-25_12:30:00.000 rxed [R] asnr 3.81
vtcodec: 2012-03-25_13:00:00.000
rxed [T] asnr 2.21
vtcodec: 2012-03-25_13:30:00.000 rxed [U] asnr
2.21
The loops were aligned approximately 110 deg which was sufficient to
reject another signal on 8970.022.
--
Paul
Nicholson
--
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