Re: LF: Digital modes comparison

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Andy,

Would a variant of WSPR be possible that uses a slower FSK rate over, for example, a 4 minute TX period? Would a half speed WSPR convey the same data in twice as long but only occupy 3Hz bandwidth? This of course assumes K1JT has nothing better to do!

73s
Roger G3XBM

On 30 July 2010 08:54, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:

Presumably "QRSS very very slow" is better still, but here this issue is the time to get data through. Andy, I assume that you're saying WSPR or JT4A give the best "data per bandwidth per given time"?

73s
Roger G3XBM

On 30 July 2010 08:17, Andy Talbot <andy.g4jnt@googlemail.com> wrote:

Try WSPR at 6Hz bandwidth  or JT4A at less that 20Hz.   They are both MSFK constant envelope schemes.

 

Andy
www.g4jnt.com

2010/7/29 Stefan Schäfer <schaefer@iup.uni-heidelberg.de>

Andy, LF,

Which digital mode could be most suited for a band where one has just an antenna bandwidth of some Hz? You know what i mean... And what could be the "gain" compared to DFCW-600. Gain means here, how far(er) could it be detected, not how much more information can i transmit within the same time.

73, Stefan/DK7FC

PS: I see that e.g. JT65 needs abt 200 Hz, so this NOT suited!


Am 29.07.2010 23:07, schrieb Andy Talbot:

It would be very interesting to see those figures normalised to a constant data rate / bandwidth.  For example, PSK31 shown at -10dB is identical to PKK63 at -7dB - well it would be, its the same modulation, just faster.   Ie plot Bits/second/Hz vs. Eb/No, then stick the Shannon limit on the graph and see which lie nearest.

 

The fact that JT65 is at the top is probably because it sits at around 0.27 chars / second, or something like 1.2 B/s.  Although even after normalisation, it would no doubt still score well up.

 

Andy
www.g4jnt.com

On 29 July 2010 21:48, John Bruce McCreath <weazle@hurontel.on.ca> wrote:

Hello LFers,

I found this while web browsing....interesting reading and Mal's favourite mode isn't top dog.

http://kb2hsh.blogspot.com/2010/05/capabilities-of-weak-signal-digital.html

I was looking for sites having info about digital modes on 1,800 kHz. and lower frequencies.

73, J.B., VE3EAR

LowFER Beacon "EAR"
188.830 kHz. QRSS30
EN93dr

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