From: DK7FC <73dk7fc@googlemail.com>
Message-ID: <53EA4F44.2080008@gmail.com>
Date: Tue, 12 Aug 2014 19:30:44 +0200
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To: rsgb_lf_group@blacksheep.org
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Subject: LF: VLF Icecast server, Raspberry PI and all that stuff
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Status: O

Hi all,

Now since i have my new garden i'm spending a lot of time reading about 
possible ways to permanently transfer "audio" data from the garden to 
the institute.

I have a direct view from a tree. This image was taken in the tree in 
about 15m AGL, 
https://dl.dropboxusercontent.com/u/19882028/20140809_211119_2.jpg

I'm planning to install a 20W solar module there in the tree as well as 
a 7 Ah accu, it is already here on my table!! ...as well as a WLAN yagi 
and a high power WLAN USB stick.

This may sound OT and it is, but recent emails about the topic has shown 
that there seem to be a few LF amateurs considering to use their garden 
as a clean remote RX location. So this may help to bring up some more 
intersting projects on VLF...MF.

Experiments will go on in small steps. But very soon i would like to 
permanently stream data to the institute to feed it into Spaclab and 
generate images for the grabbers as well as WSPR decodes and so on. All 
the Speclab instances should run on the institute to reduce the power 
consumption.

Now, at work i started to successfully establish a SPI link reading an 
ADC with an Arduino board but the Raspberry Pi seems to be the right 
choice here. I started to read about it and it sounds interesting. And 
its power consumption can be managed, it appears to be realistic. I read 
about WLAN links using normal cheap USB WLAN dongles in combination with 
the RasPI, as well as the use of cheap USB sound cards in combination 
with the RasPI. The most recent article i read was about running an 
Icecast server on the RasPI, feeding audio data (actually music but it 
could be VLF too! :-) ) via Ogg Vorbis format into the web.

I remember VLF streams by DL4YHF and/or Paul Nicholson using similar 
formats.

So my idea and plan is to:

1: Install the WLAN link over 2.4 km distance using 2 high gain yagis 
and 2 USB WLAN sticks with external antenna connectors
2: Check the data rate and availability under difficult conditions 
(rain, storm (moving tree))
3: Do some portable tests with the netbook
4: Install the solar module and batteries and solar charger (later i can 
install a few more modules if necessary)
5: Replace the netbook by the RasPI
6: Do various tests on the RasPI using 24 bit ADC with a high samplerate 
(maybe 1 Msps).

The first large goal should be to establish a permanent stream of data 
of a 192 kS/s 2 channel sound card over that distance and at lowest 
power consumption levels.

Does someone have useful ideas or comments which may be helpful?


73, Stefan/DK7FC