Новости LF/VLF/ULF/SLF/ELF > VLF (ОНЧ — очень низкие частоты) диапазон с частотами от 3 до 30 кГц
VLF: New DK7FC experiments on 17.47 kHz - Антенна из дорожного отбойника
rw3adb:
At DL0AO, we produced spectrograms and plots during the 5.17 kHz test last weekend. During the first session with the shorter guiderail antenna, signficant fading and a dip occured, most pronounced on the H-field receive antenna. Another deep dip happened immediately after Stefan switched to the long antenna, however that period may perhaps have been affected by a short retuning interruption at 12:58. Considering around 17 dB SNR in 1.5 x 3.8 mHz, the 6 dB variations seems to be too large to be explained by random noise alone. Thus we have been speculating about ionospheric variations or scintillations on a ten-minute timescale. Note that no solar x-ray or SID event had happened at the time.
Therefore I asked Stefan to repeat the test, which he did today, this time starting on the long antenna (10:39 - 11:15) and then going to the short one (11:19 - 12:10). This time the SNR was even better, and only small variations occured, perfectly within the range of noise statistics.
Best 73,
Markus (DF6NM)
rw3adb:
Hi Paul,
Thanks for your measurements.
Good idea to calculate B relative to I.
Would be interesting to see how this varies with frequency.
BTW i did now actually order one of those:
https://www.dhgate.com/product/60-v-60ah-lifepo4-60-v-60ah-lifepo4-de-litio/445395613.html#s2-21-1b;searl|3512104843
Wonder how long it takes to arrive here, and even more, if it actually
has 60 Ah at 60V, i.e. 3.6 kWh!! If so, i will order 3 more of them!...
Considering the 13 dB advantage of night/day in recent transmissions
with that ground loop antenna, at least on 8270 Hz, I'd like to try a
night transmission tonite, at 2970 Hz, trying a 7 character EbNaut
message. So far we have no message decode at ULF between DL and UK. I'd
like to reach that mile stone and think the ERP should be fine now, but
hopefully the QRN stays low enough.
Everyone else is invited to try as well!!!
73, Stefan
Am 05.04.2019 19:06, schrieb Paul Nicholson:
>
> Stefan wrote:
>
> > These were the transmissions today (+ some more parameters):
>
> Received at 5170.1 Hz,
>
> 2019-04-05_10:39,+35m: 1130m, I=2,39 A, 0.63 fT S/N -5.07 dB/1Hz
> 2019-04-05_11:19,+51m: 900m, I=2,92 A, 0.63 fT S/N -4.92 dB/1Hz
>
> Yes, the same fT in both tests. Then we have
>
> 900m
> ----
> 2.74 A -> 0.50 fT, 0.182 fT/A
> 2.92 A -> 0.63 fT, 0.216 fT/A
>
> 1130m
> -----
> 2.12 A -> 0.50 fT, 0.236 fT/A
> 2.39 A -> 0.63 fT, 0.264 fT/A
>
>
> Nothing received at 970.1 Hz.
>
> --
> Paul Nicholson
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