To: | [email protected] |
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Subject: | Re: VLF: Back on 5.17 kHz / 58 km... |
From: | Markus Vester <[email protected]> |
Date: | Fri, 30 Dec 2016 20:07:17 -0500 |
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Reply-to: | [email protected] |
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Hi Stefan,
during the last hours a good peak apperared here, around 13 dB in 63 uHz. If this is really your carrier (and not just a local GPS harmonic), tomorrow's EbNaut sequence should become an easy decode. Nice video! Best 73, Markus (DF6NM) -----Ursprüngliche Mitteilung----- Von: DK7FC <[email protected]> An: rsgb_lf_group <[email protected]> Verschickt: Fr, 30 Dez 2016 5:27 pm Betreff: Re: VLF: Back on 5.17 kHz / 58 km...
Hi VLF,
I managed to resonate my antenna on 5170 Hz. It was necessary to increase the inductance from 1.2 H to 2 H. This was done by increasing the number of iron powder cores (T106-52) from 100 to 176! It is the coil out of 10 stacked yoghurt cups that i got from Markus (many thanks again!). An image from the stacked cores into the coil: https://dl.dropboxusercontent.com/u/19882028/VLF/20161229_194850.jpg Although the number of turns of this coil is constant and the stacking height is even higher (means a lower coupling of the coils and so they must have a lower L), the inductance is higher now. So this increase must come from the cores. I clearly saw that the Q is significantly higher now, so the cores are a good choice for any VLF band. Also i need less power now. It also means that the proximity effect must be lower now (due to the lower coupling), because the Q is higher and the antenna current and the R(DC) of the coils is the same as on 6470 Hz. Now i'm running 230 mA since 14:40 UTC. I intend to run it until 8 UTC, then a first EbNaut message follows. The antenna voltage increased from 11.3 kV to 14.2 kV @ 230 mA. So far the antenna current is not really stable but it becomes foggy outside and i did not yet add the transductor to the system. Maybe i'm trying to build an ALC into SpecLab. This should work well now with the new interpreter command for the bypass factor of the delay line :-) Ah there is even a short video (6 sec, 1.2 MB) where you can see and hear (!) the coil and its internal fan on the roof while running at 14 kV: http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/VLF_coil_at_230mA_14kV_5170Hz.mp4 (hopefully the link works). Lets be optimistic, i'm announcing the first EbNaut message for tomorrow: f = 5170.000000 Hz Start time: 31.12.2016 09:00:00 UTC Symbol length: 60 s Characters: 2 CRC 16 Coding 8K19A Duration: 6h, 08m, 0s Antenna current: ~ 230 mA 73, Stefan Am 27.12.2016 12:36, schrieb DK7FC: Hi VLF,
peak_5170Hz_63uHz_161230_2336.png |
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