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Hello Wolf
The Signal you receive
is like a telephon call, some old systems use a 25 Hz a.c. with one second
duration and 4 seconds space. Nevertheless it is very difficult that these
signals can reach your receiver. Hope someone has better suggestions,
73 Cesare
-----Messaggio Originale-----
Data invio: venerdì 21 giugno 2002
19.30
Oggetto: LF: Strange signals on 25 Hz (!)
- any info ?
Hello Group,
Has anyone of this group ever heard about signals in the range of 25
Hz, like this:
- a few pulses of about one second length each, about 4
seconds pause between them
- transmitted irregularly, sometimes not
present for days or weeks
- obviously NOT related to the mains line, no
harmonics or images at 50 and 75 Hz etc
- seem NOT to travel through the
mains line.
The following is quoted from Renato Romero:
>>>Hi Wolf,
about that strange signal at 25 Hz: I receive
that signal since 1997, when I started with regular reception below 50Hz
thanks a circuit of IK1ODO with OP07 op amplifier and a big T marconi antenna.
Those strange dots appear sometimes, not always at the same time, and not
always in the same form: sometimes there are one o two dots, sometimes there
are 13 dots or more. They disappear for many days, then appear again with a
not regular schedule.
About the origin: agree with you about the not
natural origin, is clear; but what they really are ... it's a mystery.
They are not inducted by main power lines because they are not present in
the reception with a big horizontal loop (30m x 30m, 3 turns), instead of the
signals on the electric line at 1024Hz, present on air and very strong in
horizontal polarization.
They are not caused by not linear loads on the
electric line: that signals appear like a mirror with 50Hz (and 150Hz,
250Hz...): in this case there is no signal at 75 Hz.
<<<
Any ideas ? Another submarine "wakeup" transmitter ?
73, Wolf
P.S. Looking forward to Dick's Feldhell transmission. Will try
to answer in that mode, but I few its not really suited for my low-power
signal - so possibly will reply in CW.
P.P.S. Walter DJ2LF will
hold his LF talk at the Ham Radio fair in Friedrichshaven on Friday June 28,
after 16:00 local in hall 2, room "C", after an introduction by DL1VDL. ....
at least, this is written in the german CQ DL magazine. They warn about
"problems with the parking space" this year and ask visitors to use the
shuttle bus. Hope to meet you there !
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