...wow, after analysing the first 90 minutes of the transmission i
found that the best SNR is achieved without sferic blanking! So then
the hum filter and the low pass filter can be disabled too.
So far, during that noisy evening period, i'm getting about 14 dB
SNR in 185 uHz.
Unfortunately i temporarely overloaded the PC while doing the analysis,
which caused an interruption of the stream and then all SpecLab
instances did a restart.
Now the spectrogram is generated from the unfiltered and unblanked
stream and now we can already see a clear peak right on the expected
frequency, showing about 10 dB SNR.
I intend to run the carrier at least for 24 hours, if all works well.
Not sure if and how the antenna current will drop when it starts to
rain. It would have been better to decouple the DC component from the
antenna by using a big series capacitor but id didn't have one that
holds 20 kV or so.
More later...
73, Stefan
Am 07.02.2019 17:05, schrieb DK7FC:
Hi ELF ;-)
I'm glad to announce that since 15:46 UTC i am transmitting on ELF (the
real ELF, i.e. into the range of 3...30 Hz, ITU radio band
1 ) for the first time ever.
Here are the parameters:
TX frequency: 22.970 Hz
Wavelength of that frequency: 13060 km
Antenna voltage: 4.8 kV rms (+ a DC component of 7.5 kV)
Antenna current: 325 uA
ERP: 600 aW, or 6E-16 W
Call it QRP!
The goal is to detect the signal on my 3.5 km distant tree grabber,
whose E field is now working again. Since the E field probe is not to
far above the tree, the effective height is not as much as it should
ideally be, at this frequency, so the RX is somewhat deaf. Anyway i can
see the Schumann resonances and the 60 Hz power grid. So i hope it will
work.
A spectrogram which is centered on the frequency of interest in now
shown at
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
(3rd window). But maybe 424 uHz FFT bin width is even to optimistic! In
a few minutes we'll see more :-) It takes about 40 minutes until a peak
could have fully developed...
73, Stefan
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