To: | [email protected] |
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Subject: | Re: VLF: Ground loop improvements and test carrier... |
From: | Markus Vester <[email protected]> |
Date: | Fri, 5 Apr 2019 14:36:44 +0000 (UTC) |
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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...
PS: Earlier that day, the same test was done at 5170.1 Hz. But there,
the antenna current was different: 900m: T2019-03-31_12:31,+19m at I = 2.74 A 1130m: T2019-03-31_12:57,+31m at I = 2.12 A
plot_5170.1Hz_190331_and_190405.png
vlf18_190331_1345_highlighted.jpg
vlf18_190405_1230.jpg |
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