Re: LF: 1000 character EbNaut message on LF?

[DK7FC <selberdenken@posteo.de>]

Hi Markus,

You are right, it would just be a game. But maybe someone else like IZ7SLZ would receive the same message, and there, the channel would be used much more. I assume IZ7SLZ does not hear you in SSB on LF :-)
Yesterday i found that the current EbNaut decods does not accept messages longer than 200 characters, otherwise there is a message "invalid messege length" or so. So currently just the text field allows for the number 1000.
What we could do is using either QRP or an even faster mode, like 1 ms symbols :-) Could be done with the Raspi and ebkey, as far as i understand, and a CMOS XOR gate into the driver stage, for example.
Of course, the higher distances are more interesting. But who is able to produce EbNaut decodes in > 6000 km distance on LF and owns a RX with the necessary stability?

73, Stefan

Am 08.06.2017 11:56, schrieb Markus Vester:

Hi Stefan,

technically that could be made to work. But is it making good use of EbNaut's capabilities? My understanding is that it's made for messaging in SNR-limited channels, close to the Shannon / Hartley limit.

Well I remember that a few years ago you were able to hear my voice in SSB on LF. So our available SNR should be at least 10 dB higher than assumed in the calculation (40 instead of 30 dB in 0.37 Hz). With a thousand characters at 29 dB Eb/N0, someone like Mal would rightly argue that he could convey the same message faster in aural CW ;-) And a simple mode like PSK31 would be even faster...

So to fully utilize the LF channel capacity between Nuernberg and Heidelberg, we would need transmit about one million characters in 20 minutes!

On the other hand, I'd be quite keen to get five characters into Tasmania...

Best 73,
Markus


-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mi, 7. Jun 2017 21:55
Betreff: LF: 1000 character EbNaut message on LF?

Markus, Paul,

Am 07.06.2017 20:56, schrieb Markus Vester:

Considering an EbNaut sequence with e.g. N=1000 symbols,

...i first thought you are writing N= 1000 characters. Which is a good idea BTW!
Don't you like to try a N= 1000 character transmission? I would like to receive you on LF with such a message.
For example: http://abelian.org/ebnaut/calc.php?sndb=30&snbws=0.366&snmps=&code=4K19&sp=0.05&crc=20&nc=999&submit=Calculate

Paul, the calculator page does not allow to calculate N=1000, the maximum is N=999. For very long messages it would be also helpful to add the mode 4K17A to the calculator page, maybe even 4K15A.

The signal bandwidth is just 20 Hz. But my PC would have not enough RAM. But what about 4K15A, that should be fine :-)

Do you like?

73, Stefan