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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
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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