Re: ULF: Ground loop night transmission 3.0

[Markus Vester <markusvester@aol.com>]

Hi Stefan,

> Do you have an idea why the E-W cardioid result is worse than from the E field alone?

Looking at https://vlf.u01.de/VLFgrabber/vlf9.jpg we find that the noise grew much more on the earth loop (top) than on the E-field (bottom). One reason may be that our earth antennas pick up more 50 Hz harmonics - these won't interfere with your QRG directly but may raise the noise blanker threshold and make spherics blanking less effective. We could also speculate about spherics with steep incidence angle, albeit you were more or less in the middle between 1st and 2nd vertical tweek resonances (1.65 and 3.3 kHz). Anyway the SNR ratio between H to E seems to be similar to your receivers.

Of course skywave components may also have a direct effect on your signal but I don't know whether that would have been positive or negative, or in which way to extrapolate downwards. I'm very curious what would come out of a 1.65 kHz transmission during a quiet night.

> Which carrier S/N do you get from the E field?

Decoder output "carrier S/N 24.31 dB in 128.6 uHz" - should be related to carrier Eb/N0 by adding 10 log (ncharacters * 5.7).

Best 73,

Markus

  

-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mo, 15. Apr. 2019 10:32
Betreff: Re: ULF: Ground loop night transmission 3.0

Hello Markus, ULF,

Very well. Thanks for your decodes and for sharing the night :-)
Do you have an idea why the E-W cardioid result is worse than from the E field alone?
Which carrier S/N do you get from the E field? I'm getting carrier S/N: 40.62 dB in 128.6 uHz, 1.71 dB in 1Hz
The difference of our carrier Eb/N0 is 16.3 dB. But as Paul mentioned, camparing carrier S/N may be more accurate in that spectrum range.
It could be interesting to compare the SNR difference between our locations over some frequencies. If that value is reasonable constant, in the far field, then we could estimate what we can expect at 970 Hz...
My results from all 3 antennas are still looking good at that frequency:
E field: carrier S/N: 40.62 dB in 128.6 uHz
N-S loop: carrier S/N: 28.38 dB in 128.6 uHz
E-W loop: carrier S/N: 30.47 dB in 128.6 uHz

73, Stefan



Am 15.04.2019 01:33, schrieb Markus Vester:

Hi Stefan,

DL0AO H-field (E-W): Eb/N0 = 2.5 dB(car), 0.7 dB(sym),

DL0AO E-Field: Eb/N0 = 12.0 dB(car), 10.9 dB (sym). 

Our file ended a couple of minutes early with the last 12 symbols missing, causing a slightly high symbol error reading.

73 and good night,

Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>; Renato Romero <contact@vlf.it>
Verschickt: So, 14. Apr. 2019 23:13
Betreff: Re: ULF: Ground loop night transmission 3.0

Hello ULF friends,

Now i'm sitting in the car again in the deep forest. It is silent (outside!) and the sky is clear. The TX and EbNaut message is now running:

f = 2470.1 Hz
Start time: 14.APR.2019  21:00:00.3 UTC
Symbol period: 9 s
Characters: 3
CRC bits: 16
Coding 16K21A
Antenna current: 2.5 A
Duration: 02:09:36 [hh:mm:ss]

TX power at the beginning of the transmission is 492 W this time.

73, Stefan



Am 14.04.2019 14:41, schrieb DK7FC:

Hello Dreamers,

Today it feels right again, i'd like to have another exciting adventure...
After the recent successes at 2970 Hz, maybe it is possible to get something through at 2470 Hz? That's the 121 km band. So far, thge distance record at this frequency is over to DL4YHF, QRB ~ 313 km.

I'd like to try the following:

f = 2470.1 Hz
Start time: 14.APR.2019  ab:cd:00.3 UTC
Symbol period: 9 s
Characters: 3
CRC bits: 16
Coding 16K21A
Antenna current: 2.e A
Duration: 02:09:36 [hh:mm:ss]

More details regarding start time and antenna current will follow after the transmission has started.

Reports requested / welcome :-)

73, Stefan