From: Rik Strobbe <rik.strobbe@kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Thread-Topic: Re: ULF: Experimenting on 2470 Hz and 1970 Hz
Thread-Index: AQHULuL2ks7EvbklJ0ShsrMoeeawFaS1hG5+
Date: Wed, 8 Aug 2018 08:24:26 +0000
Message-ID: <1533716665257.741@kuleuven.be>
References: <165183dae71.marcocadeddu@tin.it>
In-Reply-To: <165183dae71.marcocadeddu@tin.it>
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Subject: Re: Re: ULF: Experimenting on 2470 Hz and 1970 Hz
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(I heard that somewhere in the Pentagon are getting worried...) :-D


Maybe they will offer Stefan a $$$ job ;-)


73, Rik  ON7YD


________________________________
Van: owner-rsgb_lf_group@blacksheep.org <owner-rsgb_lf_group@blacksheep.org=
> namens marcocadeddu@tin.it <marcocadeddu@tin.it>
Verzonden: woensdag 8 augustus 2018 8:33
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: R: Re: ULF: Experimenting on 2470 Hz and 1970 Hz

Hi Stefan,

amazing :-) simply amazing!

(I heard that somewhere in the Pentagon are getting worried...) :-D

73, Marco IK1HSS

----Messaggio originale----
Da: selberdenken@posteo.de
Data: 7-ago-2018 22.29
A: <rsgb_lf_group@blacksheep.org>
Ogg: Re: ULF: Experimenting on 2470 Hz and 1970 Hz

ULF,

With some delay here (attachment) are the spectrograms showing the carrier =
transmissions in 424 uHz FFT bin width. I would say it is 'O copy' and it c=
learly looks like there is some room for even longer waves to try :-)

I already checked what Wikipedia tells about SLF, https://en.wikipedia.org/=
wiki/Super_low_frequency

73, Stefan


Am 06.08.2018 16:19, schrieb DK7FC:
Hi ULF,

On Sunday, 5th 2018 i successfully crossed the far field border on 2470 Hz =
for the first time. That's the 121 km band. Later i even crossed it on 1970=
 Hz, the 152 km band. These are two new records of the lowest frequency sig=
nals generated by amateurs and received in the far field. The distance betw=
een RX and TX was 55.6 km . The far field for 2470 Hz starts at 19.4 km dis=
tance. For 1970 Hz it starts at 24.3 km distance. The RX antenna and the TX=
 antennas were loops!

By running about 100 W (PA DC input) i managed to get 910 mA antenna curren=
t on 2470 Hz into the earth loop in JN39WI. Here i transmitted a plain carr=
ier from 06:13...07:15 UTC.
Later i QSYed to 1970 Hz and here i got 910 mA as well. The 1970 Hz transmi=
ssion took place from 07:19...08:21 UTC.

Despite beeing in the middle of a large forest there was good internet conn=
ectivity and so i was able so watch my own grabber window showing the band =
activity on 2470 Hz in a spectrogram of 424 uHz FFT bin width, which is ver=
y wide for that frequency range! The spectrogram uses a Hann window and the=
 FFT window time is about 40 minutes, so it took some time until a peak bui=
lts up. But already after 20 minutes i saw that something happens! After 40=
 minutes the carrier transmission reached an SNR of about 20 dB! It was a r=
elatively quiet morning for early August.
All the VLF stream data is stored into a ~ 12 day covering buffer so i have=
 the chance to optimise the filter settings and antenna mixing in a postpro=
cessing to achieve the best SNR from the system.

For the 1970 Hz transmission there was no spectrogram available but since i=
 had internet access and a Linux notebook available, i processed the VLF st=
ream data (via SSH remote access to the storage PC) during the transmission=
 and followed the peak's SNR building up!

It clearly looks like this antenna outperforms my large inverted L in 30 m =
above the ground, at least into the ULF range! This opens up a new room for=
 experimentation on the way down to DC! :-) Now i need to get rid of these =
output transformers since they will become problematic for wide-band experi=
mentation on ULF / SLF.

Now, attached you can find two images showing spectrum peaks from the two b=
ands, out of the 55.6 km distance. The complete transmission time is here i=
ntegrated in one peak. Since the carrier S/N can also be calculated from de=
coding a '*' message in EbNaut, i also show the results for such calculatio=
n along with the whole postprocessing chain.

Spectrograms will be produced as well, but this will take a few hours here.=
..

73, Stefan


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1">
<style type=3D"text/css" style=3D"display:none"><!-- p { margin-top: 0px; m=
argin-bottom: 0px; }--></style>
</head>
<body dir=3D"ltr" style=3D"font-size:10pt;color:#000000;background-color:#F=
FFFFF;font-family:Tahoma,Geneva,sans-serif;">
<p><span style=3D"font-family: Tahoma, Geneva, sans-serif; font-size: 13.33=
33px; background-color: rgb(255, 255, 255); color: rgb(0, 111, 201); text-d=
ecoration: none solid rgb(0, 111, 201);"><em style=3D"color: rgb(0, 111, 20=
1); text-decoration: none solid rgb(0, 111, 201);"><span style=3D"color: rg=
b(0, 111, 201); text-decoration: none solid rgb(0, 111, 201);">(I
 heard that somewhere in the Pentagon are getting worried...) :-D</span></e=
m></span><br>
</p>
<p><br>
</p>
<p>Maybe they will offer Stefan a $$$&nbsp;job ;-)<br>
</p>
<p><br>
</p>
<p>73, Rik&nbsp; ON7YD<br>
</p>
<p><br>
</p>
<div style=3D"color: rgb(33, 33, 33);">
<hr tabindex=3D"-1" style=3D"display:inline-block; width:98%">
<div id=3D"divRplyFwdMsg" dir=3D"ltr"><font face=3D"Calibri, sans-serif" co=
lor=3D"#000000" style=3D"font-size:11pt"><b>Van:</b> owner-rsgb_lf_group@bl=
acksheep.org &lt;owner-rsgb_lf_group@blacksheep.org&gt; namens marcocadeddu=
@tin.it &lt;marcocadeddu@tin.it&gt;<br>
<b>Verzonden:</b> woensdag 8 augustus 2018 8:33<br>
<b>Aan:</b> rsgb_lf_group@blacksheep.org<br>
<b>Onderwerp:</b> R: Re: ULF: Experimenting on 2470 Hz and 1970 Hz</font>
<div>&nbsp;</div>
</div>
<div>Hi Stefan,<br>
<br>
amazing :-) simply amazing!<br>
<br>
(I heard that somewhere in the Pentagon are getting worried...) :-D<br>
<br>
73, Marco IK1HSS<br>
<br>
----Messaggio originale----<br>
Da: selberdenken@posteo.de<br>
Data: 7-ago-2018 22.29<br>
A: &lt;rsgb_lf_group@blacksheep.org&gt;<br>
Ogg: Re: ULF: Experimenting on 2470 Hz and 1970 Hz<br>
<br>
ULF, <br>
<br>
With some delay here (attachment) are the spectrograms showing the carrier =
transmissions in 424 uHz FFT bin width. I would say it is 'O copy' and it c=
learly looks like there is some room for even longer waves to try :-)<br>
<br>
I already checked what Wikipedia tells about SLF, <a class=3D"moz-txt-link-=
freetext" href=3D"https://en.wikipedia.org/wiki/Super_low_frequency">
https://en.wikipedia.org/wiki/Super_low_frequency</a> <br>
<br>
73, Stefan<br>
<br>
<br>
Am 06.08.2018 16:19, schrieb DK7FC:
<blockquote type=3D"cite">Hi ULF, <br>
<br>
On Sunday, 5th 2018 i successfully crossed the far field border on <b>2470 =
Hz</b> for the first time. That's the
<b>121 km band</b>. Later i even crossed it on <b>1970 Hz</b>, the <b>152 k=
m band</b>. These are two new records of the lowest frequency signals gener=
ated by amateurs and received in the far field. The distance between RX and=
 TX was 55.6 km . The far field
 for 2470 Hz starts at 19.4 km distance. For 1970 Hz it starts at 24.3 km d=
istance. The RX antenna and the TX antennas were loops!<br>
<br>
By running about 100 W (PA DC input) i managed to get 910 mA antenna curren=
t on 2470 Hz into the earth loop in JN39WI. Here i transmitted a plain carr=
ier from 06:13...07:15 UTC.
<br>
Later i QSYed to 1970 Hz and here i got 910 mA as well. The 1970 Hz transmi=
ssion took place from 07:19...08:21 UTC.<br>
<br>
Despite beeing in the middle of a large forest there was good internet conn=
ectivity and so i was able so watch my own grabber window showing the band =
activity on 2470 Hz in a spectrogram of 424 uHz FFT bin width, which is ver=
y wide for that frequency range!
 The spectrogram uses a Hann window and the FFT window time is about 40 min=
utes, so it took some time until a peak builts up. But already after 20 min=
utes i saw that something happens! After 40 minutes the carrier transmissio=
n reached an SNR of about 20 dB!
 It was a relatively quiet morning for early August.<br>
All the VLF stream data is stored into a ~ 12 day covering buffer so i have=
 the chance to optimise the filter settings and antenna mixing in a postpro=
cessing to achieve the best SNR from the system.<br>
<br>
For the 1970 Hz transmission there was no spectrogram available but since i=
 had internet access and a Linux notebook available, i processed the VLF st=
ream data (via SSH remote access to the storage PC) during the transmission=
 and followed the peak's SNR building
 up!<br>
<br>
It clearly looks like this antenna outperforms my large inverted L in 30 m =
above the ground, at least into the ULF range! This opens up a new room for=
 experimentation on the way down to DC! :-) Now i need to get rid of these =
output transformers since they will
 become problematic for wide-band experimentation on ULF / SLF.<br>
<br>
Now, attached you can find two images showing spectrum peaks from the two b=
ands, out of the 55.6 km distance. The complete transmission time is here i=
ntegrated in one peak. Since the carrier S/N can also be calculated from de=
coding a '*' message in EbNaut,
 i also show the results for such calculation along with the whole postproc=
essing chain.<br>
<br>
Spectrograms will be produced as well, but this will take a few hours here.=
..<br>
<br>
73, Stefan<br>
</blockquote>
<br>
<br>
</div>
</div>
</body>
</html>

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