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
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