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Both transmissions from SAQ were
copied nicely here in Nuernberg, JN59NJ.
Unlike in earlier years, where I
had used my LF marconi antenna for receiving SAQ, this
time it was being picked up by an orthogonal pair of magnetic
loops in the garden. This also feeds my VLF colour-direction finder,
showing blue SAQ traces: http://www.df6nm.de/vlf/vlfgrabber.htm .
As expected, the signal from the loop pointing 330
deg azimuth (left channel) was about 6 dB stronger than that on the right
channel, pointing 60 deg. SNR was approximately 40 dB in 1
Hz, with the key-up backwave about 20 dB weaker. Interestingly, during
transmitter frequency variations the signal seemed to be slightly
weaker above 17.2 kHz, so the transmit antenna resonance might have been
tuned slightly below nominal.
IQ data files at 187.5 samples/s are available at
http://df6nm.bplaced.net/VLF/SAQ/saq_iqdata_140629.zip .
If you like you can listen to the
recordings using the SndOutpt utility from the DL4YHF website, in
conjunction with simple batch commands included in the zip file. Note that
the digital 10x gain used for recording the first file turned out to be a
bit low, so I used 100x for the second one.
Best 73,
Markus (DF6NM)
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