Re: ULF: Finally 100 mA on 2.97 kHz / 65 km ULF experiment / EbNaut

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Well done (again) Stefan. Excellent!

73s

Roger G3XBM

On 14 December 2016 at 13:01, DK7FC <selberdenken@posteo.de> wrote:

Hi ULF,

My post-processing of the 4 day recording is still running, almost 50% of the data is shown on the spectrograms now.
I'm happy to confirm the successful decode of a 5 character EbNaut message over 65 km on the 101 km band, with a BIG SNR! It's the one which started on 08.DEC, 7 UTC. First there was no decode until i found that i made a mistake, the actual start of the transmission is 6:58:40 UTC, an offset of -1 symbol.
Capture in attachment. I also attach the wav file, if someone wants to play with it, the size is very small.

73, Stefan


Am 12.12.2016 14:50, schrieb DK7FC:

Hi ULF,

More news from the latest experiment on the 101 km band with QRB ~ 65 km.
Yesterday i have been in JN39VH41HL again and took all the equipment of this ULF experiment home again.
Everything has still been there and in its right place, which was the first good message. Here's an image showing the coupling of the loop antenna, 2 turns primary and about 200 turns secondary on a big ferrite core: https://dl.dropboxusercontent.com/u/19882028/ULF/20161211_123535.jpg

Even the audio recording process was still running but the USB stick was almost full. Now i have saved a 29.7 GB raw file containing the audio data for post processing. This recording is almost 4 days long. 2 SpecLab instances are now running to produce spectrograms in 424 uHz FFT bin width and 10 minute per pixel scroll rate, using a noise blanker and a 4 kHz wide filter centered on 2970 Hz.

The accus (5x 7 Ah lead gel) were discharged to 12.17V, https://dl.dropboxusercontent.com/u/19882028/ULF/20161211_123758.jpg, so it was the right choice to use these 5 accus.

The single turn vertical loop circumference is about 45m out of 1.5mm^2 cu wire and the captured area is about 70 m^2.

Now, while writing this mail, the first pixels are coming in. So far the result is looking very very good, the SNR seems to be arround 20 dB, much more than expected! See attachment. I will write a summary when all the spectrograms and eventual EbNaut decodes are available. But in the moment it looks most promising that i successfully crossed 65 km distance on the 101 km band, which was the goal. This is the path: http://no.nonsense.ee/qth/map.html?qth=JN39VH41HL&from=jn49ik00wd

73, Stefan/DK7FC


Am 09.12.2016 15:43, schrieb DK7FC:

After doing a lot of modifications here on the TX side, the effect still exists. I can't get rid of the unstable phase shown on the VLF tree grabber.

One thing to mention is that the phase seems to change slowly, no sudden phase jumps. Thus the peak is 40 dB S/N in 47 uHz. So obviously there were much less uncorrected phase glitches than expected in the first moment when i saw the effect.

Just to be sure i downgraded to the last SpecLab version, the one i used since the last month. But the effect still exists.

Next to note is the i never saw the effect in my last tests. I still have captures showing a very clear trace on 2970 Hz during the 31 km experiment. OK that was in September. The QRN levels may have been a bit higher and the signal was 7 dB weaker. So maybe the effect was just hidden in the noise?

Next i found that some SpecLab configurations seem to be corrupted by forth and back installing old (V2.90b2) and new (V2.92b2) version. So i am now using the old version and a config file that was never opened in the new version. It all seems to work fine on the TX side but i can still see the effect. BTW i even disabled the NB and checked if this makes a change. But thill the same result.

The TX schedule for the experiment is:
07.DEC: TX 2970.000 Hz (antenna current between 105...110 mA all the time) since 13:30 UTC. The recording has started about 15 UTC.

08.DEC: EbNaut 5ch, 80s, 8K19A @ 2970.000 Hz starting 7 UTC, ending 18:22:40 UTC. Then, carrier at 2970.000 Hz. Some interruptions happened in the late carrier.

09.DEC: 0 UTC starting DFCW-10800 (3h per element), 'dit' at 2969.9975 Hz, 'dah' at  2970.000 Hz. The message is 'FC'. Between F and C there is a break of 7 hours. In this time, starting 15 UTC: EbNaut 2ch, 68s, 8K19A @2970.000 Hz.

10.DEC: End of DFCW message 'FC' at 13 UTC. Then, EbNaut 5ch, 80s, 8K19A @ 2970.000 Hz starting 13 UTC (repetition of the message of 08.DEC.)

11.DEC: End of EbNaut message at 0:22:40 UTC. Then, carrier on 2970.000 Hz until 20 UTC. The recording will stopp in the late morning, due to space limitations of the 32 GB USB-stick.

>From the local recording i tried to decode the 5ch EbNaut message. But it didn't decode. I just got a '*****' message and a false decode. This is strange. The dots are quite concentrated in the two horizontal lines which indicates a stable phase. See attachment. Also the signal peak is strong and narrow. But in the red field there is nothing to see... This EbNaut message was transmitted with the new PSK config in SL. It is the reason why i will repeat the message in the end of the experiment again, using the old settings and version.

I should have done more pre-tests before starting the experiment. But now it is running. Well, the main goal is to detect a clear trace of my signal in a spectrogram running at 300 uHz or so. The signals do not look bad on the local grabber, not at all, despite the strange (propagation?) effect. I'm still optimistic...

73, Stefan