|Subject:||Re: VLF: EbNaut tonite, 'SMS' via VLF|
|From:||DK7FC <[email protected]>|
|Date:||Tue, 30 May 2017 09:07:51 +0200|
|References:||<[email protected]> <[email protected]>|
|User-agent:||Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:188.8.131.52) Gecko/20100227 Thunderbird/3.0.3|
Hi Markus, Paul,It was a long transmission with relatively short symbols. Apart from the accuracy that is required for the timing there is also a higher requirement for the accuracy of the frequency. In my attempts of getting a decode from the recent 970 Hz test i saw that there is a frequency offset of -1/(transmission time) or probably rather -1/(FFT length). I'm still not absolutely sure but maybe this also plays a role here?
A frequency offset was also observed by RN3AUS. Maybe this is not propagation but an effect that happens in the SL instance?
Something we can find out in coming transmissions.I could run something like 30...40 characters, which is close to the limits for SQ5BPF and DL0AO...
73, Stefan Am 29.05.2017 19:58, schrieb Paul Nicholson:
Markus wrote: > I managed to produce a seamless wav with 0.514 Hz samplerate:> http://df6nm.bplaced.net/VLF/fec_tests/dl0ao_170524-25_join31uHz_wav.zipStill no decode. The correlation peaks at 20.44 dB in 12.6 uHz with offsets +2058 seconds and +0.1 Hz so it looks like the settings are correct. I'm using the sample rate 0.5143924/sec from the WAV inf1 header. It's about 9 or 10dB short of decoding. The previous attempt gave 22.09 dB in 12.6 uHz so it's lost a couple of dB somewhere. -- Paul Nicholson --
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