Thanks for your answer Markus :)
la5vna S
Den 06.04.2012 19:32, skrev Markus Vester:
> Hi Steinar, LF,
>
> for an explanation, please see my mail to Alex RN3AUS.
>
> Best 73,
> Markus (DF6NM)
>
>
> Von: Steinar Aanesland <[email protected]>
> An: rsgb_lf_group <[email protected]>
> Verschickt: Fr, 6 Apr 2012 4:22 pm
> Betreff: Re: VLF: DF6NM 8970.00x
> Hi
> >> I am not familiar with this MFSK-37 mode . Where can I find some
info about it?
> LA5VNA Steinar
>
> -----Ursprüngliche Mitteilung-----
> Von: Markus Vester <[email protected]>
> An: Alex K <[email protected]>
> Cc: Stefan Schäfer <[email protected]>;
lubomir.bobalik <[email protected]>
> Verschickt: Sa, 24 Mrz 2012 8:28 am
> Betreff: Re: question about MFSK-37
> Hi Alex,
>
> my version of MFSK is no real "digimode", it's just a simple
allocation of TX frequencies to the numbers and letters of the alphabet.
I am now using frequencies #0 to #9 for the numbers, #10 as idle or
space, and #11 to #36 for the letters A-Z. Please note that since my
first experiment I have exchanged idle and zero, and now have the lowest
frequency as "0".
>
> I have tried this at three different speeds, targeted at "6000", "600"
and "60" spectrograms. For easy readout I have chosen decimal frequency
steps (1 mHz, 10 mHz, 100 mHz), and transmit times associated with whole
UTC minutes (30, 5 and 1 minutes).
>
> I have pasted my two earlier emails on the subject beneath yours. Also
attached is a calculation of character error rate vs SNR, which shows
the benefit of multifrequency MFSK (eg. "64 ch", pink curve) versus
DFCW ("2 ch", red). It is even slightly better than conventional PSK
(dashed black).
>
> Best 73,
> Markus (DF6NM)
>
> From: Alex K
> Sent: Monday, March 19, 2012 4:39 PM
> To: Markus Vester
> Subject: question about MFSK-37
> Hello dr Markus!
> I now develop the control program for my new DDS-synthesizer. I would
like to realize MFSK-37 mode for use on VLF and, probably, on LF (faster
variant). Could you inform me about the specification of this mode?
> 73 de rn3aus/Alex
>
> _______________________________________________
> Von: Markus Vester <[email protected]>
> An: rsgb_lf_group <[email protected]>
> Verschickt: Fr, 16 Mrz 2012 10:48 pm
> Betreff: VLF: MFSK-37 tests above 8970 today
>
> To explore the possibility of further two-way VLF contacts from my
home antenna, I have conducted a test in MFSK-37 mode this morning. I
was hoping to reach 0.42 mHz ("6000") grabbers using UT-synchronized
half-hour dashes. Similar to an earlier kite experiment, I used absolute
frequency encoding of characters in 1 mHz steps (0 = 8970.000, 1 =
8970.001, ... 9 = 8970.009, idle = 8970.010, A = 8970.011, .. Z =
8970.036 Hz).
>
> The plan was to transmit my complete callsign in 2.5 hours between
8:00 and 10:30. Unfortunately DHO locking failed during the first two
characters, which came out some 9 mHz low. Attached image shows what was
actually sent according to my "monitor", which is a high harmonic of the
transmitted VLF signal accidentally aliased into the LF TA window.
>
> I was pleased to find all the dashes showing up clearly as bright dots
on the OK2BVG "6000" grabber, and even left visible traces in his "600"
window. As I had also received Lubos' transmission last weekend with a
good margin in 0.48 mHz, a two-way QSO between us would probably be
feasible within a few hours.
>
> Paul Nicholson's 0.278 mHz super-sensitive spectrogram also shows the
transmission at 120 degrees azimuth, even though the dashes were really
too short to reach full SNR in this bandwidth.
>
> Results on the DK7C grabber were not quite as good, with only a single
clear dot on .006 Hz. This may partly have been due to the previously
experienced daytime minimum at our distance (180 km). Nothing distictive
was visible at OE3GHB, who is at similar distance as OK2BVG, but seems
to have suffered from a bit of local QRM at the time.
>
> Again we find that a great deal is possible with very modest means...
>
> Best 73,
> Markus (DF6NM)
>
>
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