Hi Paul,
Oh, a late reply but i see you were working hard. Interesting. And i
like the attitute not to give up so quickly. Many thanks.
Well, the transmission which took a few weeks left a signal of -100
dB(fs) on my grabber in 3.5 km. This was reproducable each day, of
course not during high noise periods.
Since a few weeks i can generate a stronger signal, up to 6 dB stronger.
Maybe this helps to find something. But i don't want to run it for many
weeks again. Furthermore i need to make changes to the system so there
is no stability garantie.
I have added plots showing the signal and noise and the phase (as
received on the tree), see
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
You can see it is now peaking -94 dB.
The antenna current plot is (inofficially) at
http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/TX.png The current is
not stable but the phase is!
I've also completed a regulator for the transductor. It tries to keep
the resonance. But the phase meter is still not working properly on 2970 Hz.
The next thing is, after the successful crossing or the far field border
in the 17km experiment i was doing another experiment in 31 km distance!
The signal is there but i am not happy with the recorded data. So i will
repeat the experiment in a few days. It is now possible to use a small
tablet PC running Windows 10 and SpecLab. SpecLab can write a single wav
file having 30 GB.
Since yesterday my transmit phase should be more stable. There were some
EMC issues in the E field feedback (SpecLab PLL). Now the feedback
signal is very strong and stable. The plot in the 424 uHz window
confirms the stability. I'm still waiting for a clear peak coming in on
the 4.1 uHz window.
There is still a lot of QRN but it can't take long to get some quieter days.
And last not least, there is some progress on the large coil which is
intended to produce a much stronger signal on ULF.
It will stay exciting :-)
73, Stefan
Am 25.08.2016 20:33, schrieb Paul Nicholson:
> Paul, any results in a bandwidth < 1 uHz ?
Not yet.
After some software alterations I've tried down to 1uHz
bandwidth (about 10 days integration) but not the slightest
trace.
Noise floor down there is around 0.003 fT. Sferic blanker
is working well.
Tried integrating separately day and night, E and H and
combined and separate, blanking out the noisy periods, etc
in various combinations. It's been a slow job even with a
quick computer - each run takes a long time to pass all the
signal through.
Disappointing, I thought we might have seen at least a hint
of signal.
I wonder if perhaps the signal is a bit too close to a
cavity mode and dispersion effects are messing up the phase.
This is uncharted territory. LWPC doesn't give a solution
down here so can't use that as a guide.
Or maybe there's just not enough ERP.
Well, I haven't given up yet but for now I've run out of ideas.
--
Paul Nicholson
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