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Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz

To: [email protected]
Subject: Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz
From: DK7FC <[email protected]>
Date: Sat, 14 May 2016 23:55:03 +0200
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Hi Paul, VLF,

Now, i've optimised the resonance a bit and can run 220 mA antenna current now! The transductor circuit is still not existing in the system so the antenna current may vary a bit. Can be watched at http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/TX.jpg
220 mA is equivalent to -36.5 dB.
Let's try again the same message.

f = 6470.00000 Hz
Start time: 14.05.2016   21:40:02 UTC
Symbol length: 100 s
Characters: 6
CRC 16
Coding 8K19A
Duration: 15h, 33m, 20s

Antenna current: 220 mA

Not the easiest time in the year but that's the challenge.
As soon as i go to 5.17 kHz we start to dive down the QRN! ;-)

73, Stefan

Am 14.05.2016 14:37, schrieb DK7FC:
Hi Paul,

Hmm, that's a pity. Maybe it would be useful to run a beacon, periodically the same message in shorter symbols, maybe 40s. A single character would be already fine, like 'R'. This would take 3:33:20 to be sent. I could do this each 4 hours.
Or i can send a simple carrier for a few days. However i want to build a circuit which keeps the antenna current constant, even during rain, so the ERP stays constant!

73, Stefan

Am 14.05.2016 12:59, schrieb Paul Nicholson:

Stefan wrote:

> f = 6470.00000 Hz
> Start time: 13.05.2016   00:00:02 UTC
> Symbol length: 100 s
> Characters: 6

I haven't been able to decode this one.   The average noise
was 3.7 dB higher than the previous successful message, so
there should still be a couple of dB to spare.

I've tried a wider range of phase search in case the
day/night phase change was more than expected.

So far it seems that 6.47 is more variable and unpredictable
than 8.27 which is opposite to what I'd expect.

-- 
Paul Nicholson
-- 


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