Hi Jacek, DC,
Yes yes, i already see a new project for summer :-)
A floating antenna will charge up to a voltage where the E field
strength is high enough to start partial discharges, something like 20
kV maybe, depending on the wire diameters and homogenity of the
arrangement, also on pressure and humidity. So there will be a voltage
limit given by the arrangement. But a higher field strength in summer
will help to charge up the antenna faster, so higher switching
frequencies are possible.
One could build/use a triggered spark gap,
https://en.wikipedia.org/wiki/Trigatron, this will hold higher voltages
and you can connect the trigger directly to a ublox GPS module running
e.g. at 3 Hz :-) I think this will give a lower jitter than when using a
vacuum relay.
Could this work over my 3.5 km path if i use my inv-L? I don't think so.
The time to integrate will be to short and there will be much QRN during
such an experiment, so the SNR will be very low. Currently (at 12.47 Hz)
i already have 15 kV DC available...
Anyway, interesting questions, there is something interesting to learn.
Maybe i will do a few experiments in summer. Building a HV divider and
measurement should be no problem...
73, Stefan
PS: Assuming 100 uA constant current 'coming from the sky', my 470 pF
antenna would charge up with 213 kV/s, so it would be possible to switch
at 10 Hz and get a 21 kV 'square wave'. Maybe the harmonics could be
detected easier than the fundamental frequency.
At 137 kHz it would be 1.5 V only (0.53 V rms). This can be switched
with a normal FET! Imagine we would switch the antenna permanently at,
say 136.172 kHz, using a FET and a ublox GPS module. Then, as soon as
the field strength is high enough, we would see a carrier on the
grabbers? We need to try that out! Amazing! What a great hobby we have!?!
PPS: For this experiment, the antenna can be series resonated, which
would help to concentrate the energy to the wanted spectrum...
Am 10.03.2019 09:58, schrieb Jacek Lipkowski:
I haven't tried this with 300m kites, but even ordinary low-band
dipoles can charge quite quickly if they are high enough, so 100uA
seems to be a good approximation. This is already comparable with the
170uA you're getting at 12.71Hz now (and which will be lower at lower
frequencies).
The only problem is the switch, but a high voltage vacuum relay (or a
few in series with a piece of fiberoptic for controlling each of them)
should be sufficient upto a few Hz.
Also note that the more charge in the atmosphere, the more ERP you
get. But it also gets more dangerous. No risk no fun on the "loomis
band" :)
VY 73
Jacek / SQ5BPF
On Sat, 9 Mar 2019, DK7FC wrote:
Date: Sat, 09 Mar 2019 22:31:41 +0100
From: DK7FC <[email protected]>
Reply-To: [email protected]
To: "[email protected]" <[email protected]>
Subject: LF: Re: Re Loomis? & ... 12.47 Hz
Hi Jim,
I hope you don't mind that i'd like to share the email with the
reflector, because i've a thought that might be interesting.
In my view, the Loomis experiment it is rather the detection of a
changing current (charge per time) on the RX site. The changing
current is
coming from a change in the static electric field, caused by the
shortcutted 'TX' antenna. Something like a current divider.
In 2010/2011 i've done VLF transmissions on my own, using a 300m
vertical kite antenna (having a special licence for that altitude). The
antenna capacity was about 1.5 nF. During an experiment in the summer
time there was a short moment when the vertical wire was floating. It
quickly charged up to some kV, which was quite noticable when i
catched and touched the wire then!! Since that time i carefully kept
the wire
grounded during such experiments.
So, it means that the wire charged up, so there must be some
continuous charge flowing onto the wire and, if the wire would be
grounded
permanently, you could probably measure a more or less stable
current, i guess it would be some 100 uA.
Now imagine someone else would rise a grounded kite in a few meters
distance. This would certainly affect the current flowing in my kite
wire.
The farer both 'antennas', the lower expressed the effect will be and
the higher the antennas, the stronger it will be expressed.
I think the effect would be much better expressed by measuring the
voltage across a 1 MOhm resistor instead, which could be done by using a
scope and some overvoltage protection!
Actually an interesting question: In the summer time, which DC
voltage could be measured over a 1 MOhm resistor when connecting to a
large E
field antenna and ground?
And, a next step: If i let my antenna charge up (floating) and then
discharge it in exact time intervals, say each second, then i should see
something at 1 Hz on a suitable receiver. This would already come
close to the experiment i'v done. I'm just replacing the 'natural charge
source' by a high voltage power supply and modulate that voltage
(with a sine wave, not rectangular).
So, to answer your question, i think that Loomis experiment was not
dedicated ELF, it was rather a broad-band spectrum that was radiated,
since
the charged antenna was discharged immediately. For a real ELF
transmission i would say that the carrier frequency has to be at ELF,
not the
modulating frequency. OK here you might say the carrier frequency is
0 and it is AM modulated...
Try to repeat the experiment! Use smaller antennas and shorter
distances. Could be interesting :-) Rise two 10m high wires in 10m
distance in
an open field. Connect one of them to a scope (1 MOhm input
resistance), protect the input with a glow lamp. Keep the other wire
floating.
Select 1 second/div. If there is a thunderstorm coming and you can
see a rising DC level on the scope, then do a shortcircuit on the other
wire. I bet you will see the voltage dropping on the scope.
73, Stefan
Am 09.03.2019 19:10, schrieb James Hollander:
Hi Jacek and Stefan, I?d like to suggest that while I can?t
say for sure there weren't ELF frequencies received in the Loomis
experiment of 1866, I?m hesitant to reach the conclusion ELF
was used by Loomis because of the following questions.
1) If the transient current that flowed when Loomis?
transmitter circuit was closed probably lasted only a few
milliseconds, wouldn?t
the modulation frequency content exceed at least the upper ELF
boundary 30Hz as impressed on the ?carrier??
2) With a 600? long TX antenna and only a galvanometer fed by
similar height RX antenna, wouldn?t any radio waves that might have been
received be shorter than 10x the wavelength for which a 600? TX
antenna is a quarter wavelength? 10x(600?x4)=24000? or about
8km. If the
wavelength is less than about 8km, wouldn?t the ?carrier? frequency
content exceed about 37 KHz?
3) Nevertheless, one might say, if galvanometer deflected
temporarily in Loomis? system, it must have detected some near-DC
content
unless some nonlinear element were in the receiving circuit. If I
Fourier Transform a damped DC transient, what is the frequency
content?
4) If there were DC transfer, wouldn't we say it's in the
nature of a current charging an atmosphere-ground capacitance through
the
ground resistance, not radio in near field ELF? Or should we say the
meaning of ?frequency? in this case becomes so fuzzy that Loomis both
did and didn?t use ELF?
5) If indeed Loomis communicated any ELF, can?t one still
radically distinguish the 12.67 Hz experiment at DK7FC as involving a
very narrow band continuous wave with 227 hours integration of this
continuous wave to detect it and make it separable from other waves
that could be generated in the ELF band?
I?m new to the subject of ELF, and would appreciate any words
of wisdom you?d like to give.
Vy 73, Jim Hollander W5EST
-----Original Message-----
From: Jacek Lipkowski <[email protected]>
To: rsgb_lf_group <[email protected]>
Sent: Sat, Mar 9, 2019 4:28 am
Subject: Re: LF: RE: RE: Almost touching the ground... | 12.47 Hz
Actually a similar experiment to Stefan's has been done already, and at
much lower frequencies (almost 0Hz :):
http://aerohistory.org/Wireless/loomis.html
In this case the power supply is from the cloud electric field and
probably had quite a few more kV than Stefan's.
Please note the DX distance.
VY 73
Jacek / SQ5BPF
From: DK7FC <[email protected]> To: rsgb_lf_group
<[email protected]>
Sent: Tue, Mar 5, 2019 12:50 pm Subject: 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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