Hi xLF !
Once again my best and sincere congratulations Stefan
We are behind you following the path you are clearing into the QRN
forest....... but "miles" away
were the way is still paved ;-)
When reading about your UFL transformer I thought about the ignition coils used
in cars
Absolutely no idea if this can be a choice to get some more current at 3KHz
But they are ready available and probably there are some big models out there
My progress to LF is halted at the moment. Have many other projects going on in
other bands
Too many bands, too many modes, too short time. This is an amazingly
multidisciplinar hobby
Keep us amazed with your achievements
73 de Luis
EA5DOM
-----Mensaje original-----
De: [email protected]
[mailto:[email protected]] En nombre de DK7FC
Enviado el: jueves, 23 de junio de 2016 14:03
Para: Renato Romero
CC: [email protected]
Asunto: LF: Re: Cumiana OOS
BTW, i am now preparing for first tests on ULF, the range between 0.3 ... 3
kHz. Tests on 2970 Hz have started. This is a completely new league. 2970 Hz is
almost 100x 'harder' than 8270 Hz. It is not easy to generate a high voltage on
my wire on that frequency. Transformers saturate and i need 6.1 H of
inductance! As a first step i am using a large ferrite transformer with 2 E
cores and a coil body. I have wounnd 3000 turns on it by hand! :-) The ferrite
material is N27 and it can handle 1V / turn at 2970 Hz without a problem. I
took 0.22 mm diameter wire. 15+ layers and each one is isolated by Kapton
insulation tape, like the old TV transformers :-) See
https://dl.dropboxusercontent.com/u/19882028/VLF/ULF%20loading%20coil%206.1H.jpg
and
https://dl.dropboxusercontent.com/u/19882028/VLF/6.1H%20ULF%20loading%20coil.jpg
I can run just 3 kV, not more. Otherwise the 'transformer' which is just a coil
in fact, is risked to flash over.
At 3 kV my ERP is about 100 nW!
So far i managed 3.5 km to my own remote grabber, you still can see the last
races at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html.
You still can see last traces from a previous 2 kV test there. The SNR was 25
dB in 424 uHz. But this is just a near field test... The far field starts at 16
km distance. It is a hard way to get that distance.
But i have built a portable E field probe and stereo audio recorder with a
Raspberry Pi. So i can take a walk in the forest and receive in really quiet
places, far away from any electricity. My next plan i to receive my own signal
in 7.9 km distance, there is a nice place :-) I have also ordered a second
cheap Neo 6M GPS module for pps and NMEA signals on the other channel during
the /p experiment. Then this will be a ideal portable monitoring system for
post processing with absolute time stamps and even location informations are
stored.
We will see. I'll come back to you when i think there could be a chance to see
a trace on 2970 Hz, maybe in a 1 uHz BW :-) The QRN is MUCH lower there,
relative to 8.27 or 6.47 kHz! Maybe this is an advantage that we underestimate
now! But the man made noise can be more problematic there, you know. So it is
good for people who like to take a walk in the forest and like to install a
hidden wire there to mount their portable RX to it and come back a few hours
later to bring it home and post process what they got :-)
73, Stefan
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