To: rsgb_lf_group@blacksheep.org
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From: Markus Vester <markusvester@aol.com>
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Date: Wed, 31 Aug 2011 14:05:20 -0400 (EDT)
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Subject: Microhertzing at LF:
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Dear LF,

inspired by the very fruitful narrowband weak-signal detections on VLF, I h=
ave set up a temporary LF spectrogram, using Rubidium locked oscillators an=
d a 0.438 mHz FFT bandwidth=20
 http://www.alice-dsl.net/df6nm/grabber/TAnarrow.jpg
(updated every two hours).

Frequency:
The receive band is currently 7 Hz wide around 137777.5 Hz, within which th=
e visible display slots can be shifted around a posteriori on request. At t=
he moment I'm showing two slots around European Loran lines
 137778.3705 Hz (GRI 7499 from Sylt and Lessay),
 137775.0000 (GRI 8000 from Slonim and Simferopol).
I chose the TA slot for the availability of other grabbers, but maybe a ded=
icated ultra-narrowband slot (eg. 10 MHz/73 =3D 136986.301 Hz) would be a b=
etter option - suggestions welcome!

Sensitivity:
Compared to my own 21 mHz TA grabber, the bandwidth reduction should provid=
e a 17 dB reduction of noise, or 11 dB versus Argo-120 at 5.3 mHz. Of cours=
e you will need to transmit a much longer dash (eg. one hour instead of one=
 minute) with good frequency stability. A GPS- or Rubidium-derived carrier =
would be the best option, but a good 1e-9 class OCXO would work just as wel=
l.

Groundwave:
In quiet daytime conditions, a radiated power of only 10 nanowatts should b=
e able produce 10 dB SNR. This could be achieved by sending 5.5 mA up a whi=
p at 1 m effective height! Or perhaps even from Lubos' ferrite antenna in T=
X mode?

Skywave:
During a few nights in Februrary 2006, John W1TAG transmitted GPS controlle=
d straight and 15-minute phase-cycled carriers. Receptions in Europe by G3P=
LX and myself revealed long periods of stable skywaves, well suited for sub=
-millihertz analysis. Some details and spectrograms can be found in=20
http://df6nm.bplaced.net/LF/slow_psk/

Now I hope to see some really feeble signals soon...

Best 73,
Markus (DF6NM)






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<font color=3D'black' size=3D'2' face=3D'arial'>
<div>Dear LF,</div>


<div>&nbsp;</div>


<div>inspired by the very fruitful narrowband weak-signal detections on VLF=
, I have set up a temporary LF spectrogram, using Rubidium locked oscillato=
rs and a 0.438 mHz FFT bandwidth <br>
&nbsp;<A href=3D"http://www.alice-dsl.net/df6nm/grabber/TAnarrow.jpg">http:=
//www.alice-dsl.net/df6nm/grabber/TAnarrow.jpg</A></div>


<div>(updated every two hours).</div>


<div>&nbsp;</div>


<div>Frequency:<br>
The receive band is currently 7 Hz wide around 137777.5 Hz, within which th=
e visible display slots can be shifted around a posteriori on request. At t=
he moment I'm showing two slots around European Loran lines<br>
&nbsp;137778.3705 Hz (GRI 7499 from Sylt and Lessay),<br>
&nbsp;137775.0000 (GRI 8000 from Slonim and Simferopol).<br>
I chose the TA slot for the availability of other grabbers, but maybe a ded=
icated ultra-narrowband slot (eg. 10 MHz/73 =3D 136986.301 Hz) would be a b=
etter option - suggestions welcome!</div>


<div>&nbsp;</div>


<div>Sensitivity:<br>
Compared to my own 21 mHz TA grabber, the bandwidth reduction should provid=
e a 17 dB reduction of noise, or 11 dB versus Argo-120 at 5.3 mHz. Of cours=
e you will need to transmit a much longer dash (eg. one hour instead of one=
 minute) with good frequency stability. A GPS- or Rubidium-derived carrier =
would be the best option, but a good 1e-9 class OCXO would work just as wel=
l.</div>


<div>&nbsp;</div>


<div>Groundwave:<br>
In quiet daytime conditions, a radiated power of only 10 nanowatts should b=
e able produce 10 dB SNR. This could be achieved by sending 5.5 mA up a whi=
p at 1 m effective height! Or perhaps even from Lubos' ferrite antenna in T=
X mode?</div>


<div>&nbsp;</div>


<div>Skywave:<br>
During a few nights in Februrary 2006, John W1TAG transmitted GPS controlle=
d straight and 15-minute phase-cycled carriers. Receptions in Europe by G3P=
LX and myself revealed long periods of stable skywaves, well suited for sub=
-millihertz analysis. Some details and spectrograms can be found in <br>
<A href=3D"http://df6nm.bplaced.net/LF/slow_psk/">http://df6nm.bplaced.net/=
LF/slow_psk/</A></div>


<div>&nbsp;</div>


<div>Now I hope to see some really feeble signals soon...</div>


<div>&nbsp;</div>


<div>Best 73,<br>
Markus (DF6NM)</div>


<div><br>
<br>
<br>
&nbsp;</div>


<div style=3D"CLEAR: both"></div>
</font>
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