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Jose,
Just rcd - thank you for your most informative
summary.
Excellent work.
73, Rog.
----- Original Message -----
Sent: Thursday, August 02, 2007 5:37 PM
Subject: LF: 500 Recent daytime test
Hello all,
Some days ago I asked for cooperation to make a
test of daytime propagation on this band, and the colleagues Finbar-GI4DPE,
Mike-GW4HXO and Rog-GW3UEP were kindly running their CW beacons for such a
test.
The purpose of the test was to corroborate, with an
ERP as low as 0.1W, that daytime reception by ear, for a 1000km sea path, could
be possible. According to the family of curves of the ITU Rec.368, the expected
field strength for 0.1W, for this kind of sea path, is roughly -14dB(uV/m).
Unfortunately I couldn´t make measurements, with my heavy "messempfänger", of
the incoming signal either the external noise field strength at the receiving
site but, assuming the previously mentioned signal level for GW4HXO ( only 4 km
land mass), an external noise in the range of -27 to -33 dB(uV/m) for 1 Hz, ( in
my noisy urban QTH it´s around 10 dB higher), and considering some 20 Hz for the
BW human ear, can be obtained an audio signal to noise in the order of 5dB.
Regarding to the Rog´s path, I think his power is something lower than the
Mike´s one, and besides there are 60 km of land mass, so no possible reception
by ear was possible. For the path with Finbar there are 300km of land mass to be
added to 1000km of sea, so the resulting path loss is enormous.
As a personal curiosity, I´ll try to calculate, for
this last case, and for other UK mixed paths, the expected FS according to the
Millington method recommended by ITU.
On the other hand, I think that QRSS and CW beacons
are very useful in order to study, or simply to monitor, the radio propagation,
but I´d like to mention again, for the CW ones, the convenience to transmit
a long dash, equal or longer than 10 sec, to make possible plottings with
weak signals; I think it would be better a speed lower than 10 wpm.
73 de José, EA1PX,
IN53ti
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