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Re: LF: MF WSPR remote RX experiments

To: [email protected]
Subject: Re: LF: MF WSPR remote RX experiments
From: DK7FC <[email protected]>
Date: Wed, 04 Feb 2015 00:19:27 +0100
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Hi Markus,

It is still a test on the same antenna like the normal MF grabber. Yesterday i have been in the garden, trying to get a connection with the raspi. BTW this system is consuming 220 mA at 12V now. Got no internet access. Connected the netbook, found the link, connected (5 of 5 bars SNR) but "The DNS server does not answer"... Will solve that soon. But it was a sunny day and fun to climb into the tree after a few months. See this image: https://dl.dropboxusercontent.com/u/19882028/MF/20150202_153957.jpg

Yes the hard test will be in the afternoon :-) Hopefully i can check this very soon. And i like to run the system for a few days...

73, Stefan

Am 04.02.2015 00:07, schrieb Markus Vester:
Hi Stefan,
 
interesting, great experiment!
 
I've placed your two MF grabbers side by side. Actually except for the different scroll rates, the two spectrograms look surprisingly similar. Even some of the interference seems to be common to both (eg. the unstable line on 475.35 kHz) - I would have thought this is a local one from your building but apparently not so.
 
Background noise level also seems to be similar now. But if there is an improvemant it may show up more dramatically in the daytime when the external noise floor should be much lower.
 
Best of luck,
Markus 

From: DK7FC
Sent: Tuesday, February 03, 2015 11:45 PM
Subject: Re: LF: MF WSPR remote RX experiments

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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