Hi SLF,
Attached is a spectrogram from a reprocessing of my recent DFCW-5400
transmission down on 270 Hz. The SNR reaches up to 30 dB in that
bandwidth. It shows that messages could be exchanged up to 10 km
distance if there would be someone with a suitable RX/TX system. Now
after 'saying hello' on that 1110 km band, i'll continue my trip to the
end of the spectrum. Next station is near 80 Hz, TXing deeper than
ZEVS. Maybe i'll come back to 270 Hz from the ground loop antenna, if
the coming experiments on 470 Hz will be successful.
73, Stefan
Am 06.11.2018 14:55, schrieb DK7FC:
SLF,
Now, a 30 character EbNaut message has been sent over the short path.
Reception was excellent, with several dB over the decode limit. Even
with that pW power range, some distance can be crossed. With the ham
density in my region, it should be possible to reach someone else
(theoretically!) who can copy the message and attempt for a split-band
two way contact.
Capture attached.
73, Stefan
Am 05.11.2018 23:14, schrieb DK7FC:
Well, today, i did a first step into the ITU radio band 2, SLF.
Since 21:00 UTC i'm transmitting on the INV-L on 270.01 Hz. The
antenna current is just 2.5 mA. The ERP is about 6 pW.
Almost nothing but anyway a trace becomes visible now on my RX on the
tree in 3.5 km distance
(http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html)
Of course this is a near field experiment. There, on the 1110 km
band, the far field begins at a distance of 177 km.
On the transmitter site i'm using the modified 5 kV mains transformer
that was used to produce 5 kV at 970 Hz. Now there is a series
capacitor of about 20 uF applied to the primary winding. Together with
internal reactances this maximises the peak of the fundamental
frequency of the output voltage.
The goal of this first experiment is just to put the foot into this
part of the radio spectrum. And to do some pre-tests, trying to
optimise filter and blanker settings for future tests.
In the end i'm planning to work on that frequency from the ground loop
antenna, which is still in the near field, but anyway :-)
73, Stefan
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DFCW-5400_270Hz.jpg
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