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Message-ID: <3.0.3.32.19990714223318.006f6764@mailer.inrete.it>
Date: Wed, 14 Jul 1999 22:33:18 +0100
To: rsgb_lf_group@blacksheep.org
From: "M. Bruno" <spin@inrete.it>
Subject: LF: Strange ELF signal (not LF...)
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Hello all.

This message may be off-topic here, but I don't know of better
places to talk about this.

By first, the facts.

A dear friend, Renato IK1QFK, since many years monitors the
natural radio signals in the 0-20 kHz spectrum. He has a variety
of electric and magnetic probes (antennas?) and a lot of 
successful recordings.

He found a man-made signal with the following charcteristics:
Frequency: around 1025 Hz
Format: on/off modulation, CW-like. Bit lenght about 0,64 s.
Strings of 20 seconds, or about 5 seconds (32 or 8 bits ?).
Time: starts about 20-30 seconds after the hour. Not every
hour, but usually I see it at 2000z and 2100z. It lasts sometime
for minutes, with several different 'messages' separated by
tens of seconds of silence. We have no evidence of a 'QSO' or
a replying station.

The signal was evident with the E-field antenna. After some
discussion I proposed to look at the mains network, and the 
signal is there, loud and clear!

It is exactly midway between the 1000 Hz (weak) and 1050 Hz 
(stronger) harmonics of the mains. The amplitude varies with 
time and day, and is approx. -70 dB respect to the 50 Hz. 
The amplitude is confrontable with the 21th harmonic at 1050 Hz.

To observe the signal, use Spectrogram, connect the SB input 
to the mains, via a transformer and some attenuation network. 
I use a 24 V winding, followed by a resistive divider and a 3 nF 
capacitor to act as high-pass filter and reduce the 50 Hz component.

------------------

Now, the questions: who? why? how? where?

The signal amplitude between my QTH and IK1QFK is the same.
We live at about 15 km distance. Friends at our ENEL (the Italian
Electricity Board), involved with high voltage line signalling, exclude
any involvement of telecontrol or signalling systems. They use LF.

-70 dBc means about 600 mV of signal over the mains. The impedance
of the network may not be completely different at 50 Hz and 1 kHz ...
and may be that at 1 kHz it is even lower, because of the capacitances.

Assuming as an hypothesis that the signal propagates like the 50 Hz,
the total installed power in Europe should be some figure in the order of
10^11 W and the power involved with the signal should be big (tens of kW ?)

The signal is also visible in E-field, connecting the Marconi "T"
to the SB line input via an audio preamplifier. Sometime it is
even clearer in E-field than on the mains.

We will appreciate reports from OMs in other countries and from
other places in Italy (IK5ZPV ? HB9ASB ? you are the nearest).

One last thing: this signal is not alone ...

Sorry for the bandwidth, but we are really puzzled.

73 - Marco IK1ODO
spin@inrete.it