Date: Tue, 3 Jul 2018 09:44:18 -0230 (NDT)
From: jcraig@mun.ca
To: rsgb_lf_group@blacksheep.org
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 <5B38D8E1.2020108@posteo.de>
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Subject: Re: VLF/ULF: Improved grabber from the tree...
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Hi Stefan,

Well done on your setup; it's  inspiring.  On the day of the SAQ=20
transmission, the 10 uW sigs on 8270.0075 Hz could be heard at 3.3 km
which is a new distance record for me on VLF CW. The TX is back to
an unmodulated carrier again.

73 and GL
Joe

On Sun, 1 Jul 2018, DK7FC wrote:

> Hi VLF,
>
> In the last weeks i finally installed the octo-soundcard for the raspberr=
y pi=20
> on the tree. Now i can listen on 6 channels simultaneously. So now i am a=
ble=20
> to track the signals of both of my orthogonal VLF loops mounted in 18m ab=
ove=20
> the ground.
>
> The raspi is running vlfrx-tools. A GPS module provides accurate timing f=
or=20
> the system, so it does not depend of an available internet connection=20
> providing the ntp service. The sample rate is corrected on the tree and a=
=20
> stream is generated which includes timestamps.
> 2 channels are used for the MF loops. Another 2 channels is used for the =
VLF=20
> loops now and one channel is for the 1PPS+NMEA. So there is 1 channel lef=
t!=20
> The idea is to build an E-field RX for VLF so i can generate a 360=C2=B0 =
RDF=20
> spectrogram. But it would also be nice to have something for LF... There=
=20
> should be even more channels on the input :-)
>
> Anyway, now i can already generate RDF spectrograms. They are hidden on m=
y=20
> grabber page,=20
> http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
> If you click on one of the spectrograms, it will switch to the RDF mode. =
Not=20
> all of the images are available in RDF mode. The other channel show the=
=20
> signals of the E-W loop. I should add a 3rd image showing the N-S loop bu=
t i=20
> have to see where i can find another computer running a few more SL insta=
nces=20
> :-)
>
> So far i'm still fighting with stream interruptions. Streaming 5 channels=
=20
> (two of them are vorbis streams and three of them are flac streams (lossl=
ess=20
> compression!)) means a significant data rate over the 2.4 GHz WLAN link.=
=20
> Thus, another task for the coming days is to move to 5 GHz where higher d=
ata=20
> rates should be no problem.
>
> I'm saving 100 GB of the data of the VLF loop so i can post-process the=
=20
> signals of about the last 2 weeks (the stream is resampled to 24 kS/s). T=
hat=20
> means i can configure a 'totary loop', software based.
>
> So now, if VO1NA and IW4DXW transmits a message in the same time, i can w=
atch=20
> for both of their signals and even 'turn' the loop for the best S/N for e=
ach=20
> station :-)
>
> Joe's carrier has been very weak here and the common dark time is very lo=
w=20
> and but the QRN is very high. So there are doubts that i will detect the=
=20
> carrier but it may be worth a try :-)
>
> If someone else wants to try to transmit down there, don't hestitate :-)
>
> 73, Stefan
>
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