Hello Jim, Luis, Jim,
thank you for the kind words. Well, yes, i would like to try 1 Hz and
less, and try to transfer a message below 1 Hz! But my soundcard cut's
off at 2 Hz, see attachment. Maybe this is due to the components on the
soundcard and can be extended downwards. But first i would try 2.97 Hz
or so. Currently i'm at 6.47 Hz but the E-field RX has a bad contact up
in the tree again. I need to find and solve that problem.
For the PA, doing 1 Hz or even 1 mHz is no Problem and i can hold the 5
kV rms at any frequency towards DC, including DC :-) If i can find the
time soon i will draw the schematic of the ELF PA and will show it here.
Currently i'm generating a spectrogram in SpecLab, running on a wav
file (mono, resampled to 240 S/s) that covers 8 days of the carrier
transmission on 12.47 Hz. It is set to 22 uHz FFT bin width and 3
hours/pixel scroll rate :-) Since SpecLab can do it in real-time only
it will take 8 days to complete the spectrogram, but never mind, we
have so much time, don't we?! I will show the result in a week then ;-)
But i already see that the trace is very strong, mch better than
expected and exactly on the frequency (as expected). Anyway it is good
to see that all this works so well in that frequency range. It looks
like a 10 km distance would be possible, if there would be a radio
amateur with the necessary equipment and motivation (both very hard to
find!).
On the tree i have some self-made QRM below 10 Hz. This comes from the
AM on the 5 V supply voltage. The culprit is the WLAN-stick and its
data packages, consuming a few 100 mA but only durng the times where
data is sent. It was filteres by a parallel C of 20 mF (low ESR) near
the E field amplifier and a series L of about 1 H. But there's still
that rest below 10 Hz. The E field amplifier uses a typical J310
circuit.
Now i have the idea to play with an LMP7721 Op AMP
instead, which should provide some rejection of the AC component of the
supply voltage. Will see if this works well on the tree, at least i
have a good signal to compare with. It would even allow to build in
some gain below 50 Hz, on the cost of a changing phase...
I wonder what distance could be made on the earth loop at ELF! I bet it
will work much better because i can keep the antenna current constant
down to DC and my PA already works below 10 Hz...
More soon.
73, Stefan
Am 06.03.2019 17:46, schrieb [email protected]:
Stefan,
Echoing Luis' comments this seems an inspiring journey into a wilderness
area. If by ground you mean 0 dBHz, I will sincerely be on the edge of my
chair waiting for your first spectral sub-surface (-0.1dBHz?) experiment.
Fortunately the natural/cultural background has been characterized for your
background-cancellation pleasure to -140 dBHz (see attached or page 4 of the
link below), well below spectral ground.
Natural/cultural background spectrum 45 dBHz to -140 dBHz: page 4 of:
https://igpppublic.ucsd.edu/~cathy/Publications/Preprints/spectrum.pdf
73,
Jim AA5BW
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of VIGILANT Luis
Fernández
Sent: Wednesday, March 6, 2019 3:19 AM
To: [email protected]
Subject: LF: RE: Almost touching the ground... | 12.47 Hz
Hi ELF
Absolutely outstanding achievement Stefan
A different world and truly physics experiment. Then you will have to hear
those blind minded regulators claiming to state rules at this frequencies.
Always recurrent to contest, QSOs and bandplans ... LoL!!
But that is all you can expect from the average HF byassed amateur-lawyers
we already have at IARU
This is like Antarctica. Mother nature and virgin territory for the real
pyoneers who dare to explore it
My pleasure and deepest recognition for your success :-)
73 de Luis
EA5DOM
-----Mensaje original-----
De: [email protected]
[mailto:[email protected]] En nombre de DK7FC Enviado el:
martes, 05 de marzo de 2019 19:45
Para: [email protected]
Asunto: ELF: Almost touching the ground... | 12.47 Hz
Hi ELF friends,
During the last 2 weeks i've done another experiment on ELF, this time on
12.47 Hz, the 24 Mm band (wavelength 24057 km). Again i've crossed the local
distance of 3.5 km. That's the lowest frequency i've ever been and it feels
like i can see the ground already :-) The dimensions of everything down
there are extreme. I've integrated 227 hours of a carrier transmission into
one spectrum peak, it is shown in the attachment in 1.25 uHz. This carrier
could have transferred an EbNaut message of nearly 100 characters.
The ERP was 50 attowatt or -163 dBW and the antenna current was 170 uA only,
despite about 5 kV antenna voltage.
I'm now trying to put a step below 10 Hz but the RX antenna becomes less
efficient with each Hz.
73, Stefan
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