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Excellent Jay, thanks very much! I am really happy
about this result. Attached is a spectrum graph,
showing your peak at 3:16 UT, with about 12 to 14 dB SNR in the 0.438 mHz
FFT.
Do I understand you correctly in that you transmitted
a continuous carrier, without a frequency step? Then the apparent 3.8 mHz shift
must have been a transient propagational Doppler effect.
Remarkably, this lines up with observations of John Andrew's tests in
2006, which had also shown two long stable runs, with a dip and rapid
phase change inbetween. The dip seems to roughly coincide with midnight
crossing over the middle of the path, but I'm not aware of any simple physical
explanation for this.
BTW Your transmit situation must be similar to mine: I
have about 200 W available into a Marconi antenna, which is about 0.1
percent efficient now, and up to twice that in a cold winter
night.
Best regards, and thanks again for the
test
Markus (DF6NM)
Sent: Sunday, September 04, 2011 1:27 PM
Subject: Re: LF: Weak signal on 137780.3
Markus
The mystery signal was from WD2XNS ... you have the
time and frequency perfectly correct and the color DF also provides
corroborating evidence. Note that there was no break in the
transmission. The frequency is controlled by a GPS disciplined
oscillator (accuracy about 13 ppt). Transmitter power was 200 watts ...
radiated power is not known. During winter, with frozen ground, additional
radials, lower R and less foliage, the radiated power would have been
about 0.5 watt. Expect last night's test would be at least 3 - 6 dB
(maybe more) below that level.
Jay W1VD WD2XNS WE2XGR/2
----- Original Message -----
Sent: Sunday, September 04, 2011 4:45
AM
Subject: Re: LF: Weak signal on
137780.3
The mystery signal was received between about
0:15 and 3:30 on 137780.310, with a 3.8 mHz downward shift from
about 1:30 to 2:15 - somewhat reminiscent of a DFCW "GM". Greenish colour
indicates southwesterly origin. The attached screenshot was taken at 8
UT, timescale is 10 minutes per FFT.
I checked the other available TA grabbers around
4 UT, but no trace of the mystery signal.
73, and have a nice sunday,
Markus (DF6NM)
Sent: Sunday, September 04, 2011 5:39 AM
Subject: LF: Weak signal on 137780.3
LF,
there seems to be a signal on 137780.300 Hz,
about 60 nV/m here.
Wondering whose it may be...
Best wishes,
Markus
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