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Re: VLF: Ground loop improvements and test carrier...

To: [email protected]
Subject: Re: VLF: Ground loop improvements and test carrier...
From: DK7FC <[email protected]>
Date: Fri, 05 Apr 2019 18:14:39 +0200
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Hello Markus, VLF, ULF,

Thanks for the todays tests and the good cooperation. Amazing what we can do meanwhile, watching smaller variations of the signal levels, which would not be possible from my large INV-L antenna because we could not get such an SNR in that bandwidth.

These were the transmissions today (+ some more parameters):
T2019-04-05_10:39,+35m: 5170.1 Hz @1130m, I = 2,39 A, P =  461 W, C = 767 nF
T2019-04-05_11:19,+51m: 5170.1 Hz @900m, I = 2,92 A, P = 566 W, C = 867 nF
T2019-04-05_12:14:20,+10m: 970.1 Hz @900m, I= 3.09 A, P = 613 W, C = 10.2 uF
T2019-04-05_12:30,+38m: 970.1 Hz @1130m, I = 2.49 A, P = 500W, C = 7 uF

73, Stefan

Am 05.04.2019 16:36, schrieb Markus Vester:
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
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