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)



-----Ursprüngliche Mitteilung-----
Von: DK7FC <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Mi, 3. Apr. 2019 20:26
Betreff: Re: VLF: Ground loop improvements and test carrier...