Re: LF: EbNaut on LF

[Markus Vester <markusvester@aol.com>]

Hi Joe,

yesterday night (Aug 18/19) there was high QRN well into the wee hours. After some tweaking of the time offset, I managed to extract a single marginal decode from the 4:15 sequence.

I was still wondering why the decode was weak in terms of EbN0, despite an already visible agglomeration of dots in the phase plot.  Comparing the carrier phase before and after the sequence allowed me to rule out receiver glitches. The real reason is probably that compared to the mostly used 8K19 code, 4K19 has less spread and longer symbols, which at same EbN0 shows up better in the constellation plot and squared-symbol spectrum. Shorter codes are also easier on timing accuracy, CPU and memory, but don't go down quite as deep in EbN0 as longer codes do. In any case, your net data rate of about 20 characters per minute is quite impressive...

Last night conditions were much better, with stronger sigs and low statics from the beginning. The 00:15 (Aug 20) transmission immediately came up with EbN0 = 7.7 dB.

Best 73,
Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: jcraig <jcraig@mun.ca>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Sa, 20 Aug 2016 12:00 am
Betreff: Re: LF: EbNaut on LF

Dear Group,

One more operation tonight starting 2300 and every 15 mins.
150 watts 2 amps RF. 137.477 kHz, 1432 0.2s symbols, 4K19A.

73
Joe VO1NA

08190416c_1053.19s_sym.png
Description: PNG image

08190416c_1053.19s_result.png
Description: PNG image

08200016_sym.png
Description: PNG image

08200016_result.png
Description: PNG image