Date: Fri, 16 Jun 2017 00:04:14 +0000 (UTC)
From: John Fisher <johnfish837@yahoo.ca>
To:  <rsgb_lf_group@blacksheep.org>, Renato Romero <contact@vlf.it>
Message-ID: <1476723217.13585631.1497571454694@mail.yahoo.com>
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Subject: Re: ULF: New experiment on 970 Hz, results (3/3)
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Fantastic work, Stefan!

John
73 de VA3VVV
Toronto, Canada


--------------------------------------------
On Thu, 6/15/17, DK7FC <selberdenken@posteo.de> wrote:

 Subject: Re: ULF: New experiment on 970 Hz, results (3/3)
 To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>, "Renato Romero" <contact@vlf.it>
 Received: Thursday, June 15, 2017, 7:02 PM
 
 
 Hello dear ULF friends, 
 
 
 Here is my summary of the latest experiment on ULF
 which took
 place from 16...20 of May 2017. The experiment was to
 transmit
 for 90 hours on near 970 Hz, a wavelength of
 309 km.
 
 
 The transmitter site was my normal inv-L antenna, 30m above
 ground,
 about 70m long. A modified HV mains transformer, driven by a
 homemade
 linear mode class-AB PA, produced 5 kV on the antenna
 wire.
 This results in 15 mA antenna current and an ERP of about
 3 nW.
 The signals were generated by SpectrumLab software. The
 transmit signal
 was locked to a GPS reference.
 
 
 The receiver position was in JN49LN91GB, that's a
 distance
 of 27.2 km to the transmitter site. This is the path
 between TX and
 RX: http://no.nonsense.ee/qth/map.html?qth=JN49LN91GB&from=jn49ik00wd
 
 This time, an active E field antenna was used for reception
 because
 27.2 km distance is still in the near field for that
 wavelength! It is about 55 % of the far field border
 distance.
 
 The signal was recorded by a Raspberry Pi running a USB
 stereo
 soundcard. The second channel was recording a reference
 signal
 containing PPS pulses and NMEA data from a NEO-6M GPS-module
 for
 compensating sample rate drift and sample losses. The data
 was written
 into a  ~ 30 GB file on an USB stick connected to the
 Raspi.
 
 
 The data was post processed afterwards. Spectrograms in
 bandwidths of
 424 uHz, 212 uHz, 106 uHz and 47 uHz were generated. A few
 optimisations were done to find suitable settings for a band
 pass
 filter and noise blanker.
 
 The first time, two EbNaut messages were transmitted, see
 the
 transmission plan:
 
 
 May, 16th:
 
 14:43:08 UTC: Start of recording. Carrier on 970.005 Hz for
 the rest of
 the day.
 
 May, 17th:
 
 Continuing of the carrier transmission, for the whole
 day.
 
 May, 18th:
 
 00:00:00 UTC: EbNaut, 5 characters, 16K21A, CRC4, 100 second
 symbols.
 Taking 24 hours exactly. The message was
 "DK7FC"
 
 May, 19th:
 
 00:00:00 UTC: Carrier on 970.01 Hz, for the whole day.
 
 May, 20th:
 
 00:00:00 UTC: EbNaut, 2 characters, 16K21A, CRC3, 60 second
 symbols.
 The message was "73".
 
 09:20:00 UTC: End of EbNaut transmission.
 
 10:27:05 UTC: End of recording.
 
 
 Here are all spectrograms and images: https://www.dropbox.com/sh/n7k0il4pp6vqbbc/AACbfwbN4TQ1RrS6YIEDYzMpa?dl=0
 
 
 The signal shows up to 15 dB in 47 uHz. There is no
 QRM in +-
 10 Hz but the QRN was extreme, including local thunderstorms
 on the
 19th. Several times there were lost samples into the
 recording but
 SpecLab corrected that nicely, so the spectrograms look as
 expected.
 
 Fortunately both EbNaut messages were decoded after a
 longer
 series of decode attempts. So there can be no doubt that
 this was a
 successful experiment. 
 
 
 The next attempt will be to reach the far field border
 distance in >
 49.3 km. I will need about 10 dB more radiated power, which
 is possible
 with some effort. Maybe an improvement on the receiver site
 will help
 to rise the SNR a bit more!
 
 
 73, Stefan/DK7FC