Hi MF,
I have improved my new /p receiver for MF.
Also Wolf followed a suggestion for SpecLab and released an updated
version, many thanks for the service! The suggestion was to add a button
to automatically restart the connection to a web stream.
This function is important for my Raspberry VLF/LF/MF link, in case the
is a short loss of the connection. Re-connecting works very well and so,
the "near end" of the system, i.e. the link: data-stream ->
Spectrogram/grabber/tone/VAC/WSPR et. al. is complete!
So, SpecLab reads the stream, generates Spectrograms, CW tone, WSPR
passband inclusive frequency conversion to 1500 Hz "dial", jpgs and
uploads to the web server, all i need :-)
I set up a new experimental grabber at
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_remote_Grabber.html,
now showing the received data stream of MF.
I'm excited by the rx performance now (homemade DC). The dynamic range
is 100 dB and the band noise at -80 dB f.s., i.e. 80 dB range. Maybe
this even allows to transmit without overloading the RX if it is in 2.4
km distance?
Just some thoughts for the moment ;-)
73, Stefan/DK7FC
Am 30.01.2015 18:45, schrieb DK7FC:
Hello MF,
I've continued with tests for my remote RX station.
Right now i am running a Raspberry pi on a 7 Ah battery. It drives a
WLAN stick and a simple USB sound card, feeding audio via a vorbis
steam through the web. A MF receiver (LO = 461 kHz) is running on the
same battery. The RX is connected to the same antenna where my MF/LF
grabber is connected to. Ah and the Raspberry pi is powered by an
external switch mode regulator, 12V=>5V! All in all this consumes
about 250 mA @ 12V.
I am playing the vorbis audio stream (about 220 kbps) directly in
SpecLab where i can see the full MF spectrum. SpecLab is running a 2.5
kHz wide band filter and frequency converter feeding a virtual audio
cable. Finally this is connected to WSPR-X... Now i can compare the
SNR difference on both, the grabber RX and the remote-RX plus web
data stream. The receivers are technically nearly identical as well as
the filter settings.
There is some time delay but it is not problematic, no correction
needed for WSPR. I'm getting quite good results from the first
attempt, a SNR difference less than +- 1 dB.
The remote system is not running in the garden now, just a local test.
WSPR reports on MF via web streaming are coming in at DK7FC/RPI.
The test is running for a few hours now :-)
73, Stefan/DK7FC
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