The old one does not show the slope at 1pps signal.
The PC that I'm using for the test grabbers is too slow and I
can't go at 47uHz with it: the waterfall never appears. Trying with
newer and more powerful PC all is ok.
To be continued...
73, Max IK0VVE
...here some of my HAM Radio projects...
Sat, 07 May 2016 00:35:41 +0200
Re: LF: testing VLF grabber
Your motivation is pleasant. The stuff we all need to reach exciting
results together :-)
Am 06.05.2016 23:30, schrieb Max IK0VVE:
I do not have time to reach you that you already run away to
lower frequencies, HI.
Yes, sorry, it's a bit unpredictable what i'm doing these days but the
are more transmit stations on 8.27 kHz. Also i will come back of
course. And by this way i keep the center frequency 8.27 kHz free for
other TX stations. I can try to decode EbNaut on 8.27 when transmitting
on 6.47 during the same time.
I passed the last nights to try to discipline my audio board
with my 1pps GPS... nothing to do, I've tried all, levels, phases,
etc... I followed the Wolf's tutorial without success. I suppose duty
cycle is to low. I'm waiting for a new GPS so I'll try with that or in
the worst case with an OCXO+GPS 10khz.
Did you watch the signal on the oscilloscope and on the scope of
SpecLab? I need more precise infos to give some advice, maybe a capture
of the scope and the schematic how you coupled the module to the input.
So only for test now I'm pointing to German LF station DHO.
Inserted BP and NB and moved to about 100uHz the resolution of the
Did you enable "1 pixel per FFT bin"? That would be recemmended.
Tomorrow a little trip, not so far, to an Ham friend to listen
if his zone is quieter than where I live.
I'm interested to your Raspberry Pi remote system, can we get
Wow, of course that is a large project and i could write for hours. But
a rough overview should be no problem:
-The Raspi 2B is used
-I'm using a 2.4 GHz link, with this yagi
over a distance of 3.5 km in combination with USB WLAN Sticks (ALFA
AWUS036NEH running in 'g' mode) connected to the Raspi.
-Two stereo USB soundcards are connected to the Raspi, one for MF, the
other for VLF. The samplerate is 48 kS/s.
-The radio signals of MF are converted to a range of the soundcard
(0...24 kHz), VLF comes in directly.
-Darkice and Icecast2 software is running as a web radio, vorbis stereo
stream. Each stereo stream needs 20% CPU power, about.
-For VLF, i'm using the right channel to transfer 1 pps + NMEA signals
from a cheap GPS module (13 €) which consumes just 40 mA at 3.3V. This
allows to get an ultra stable signal which is necessary for the 47 uHz
-On the other end, SpecLab is playing the stream from it's IP adress,
generates the first spectrogram ('wideband' on the top of the page
and feeds the audio signal to VAC1. All other SL instances take the
audio signal from VAC1 then, so the stream has just one client.
-There is a battery voltage and current monitoring so i can all the
time monitor the energy situation on the tree. The curves are displayed
(I nned to cut some branches because the sun is now shining from a
higher angle, so there is some shadow on the solar modules in the
afternoon. But i don't want to cut them :-) In winter it is no
-There are additional circuits for protecting the batteries from deep
discharges and there is a homemade accu charger that has a temperature
regulated cutoff voltage.
-Currently 2 solar modules, 50Wp each, are used. And 3 lead gel accus
- So far i prefer loop antennas for MF and VLF. Two orthogonal loops
for each band, allowing RDF spectrograms. MF is running at
, VLF is not so easy in RDF because the second channel is occupied by
pps+NMEA. But there must be a solution!
- In previous versions of the system i used a bistabile relay to switch
antennas remotely. That worked very well.
-The power consumption of the system is about 3W
now since two
soundcards + the GPS module + 40% CPU power is running permanently.
Don't know if you already started to play with the Raspi or if you are
skilled in Linux. I spent dozens of hours to get it running as it is
now. But there were great success moments many times. And i find the
system availability is quite good, better then expected in the
I don't want to miss the project a single day :-)
73, GL, Stefan