Hello Paul, ULF,
Thanks for the efforts. 11.9 dB, that sounds good. For a valid detection
you said we need 14 dB SNR. Anyway, quite close and it is unlikely that
it is a noise peak.
Actually this is quite amazing, considering the many days of stacking of
a several hour long transmission we needed to produce 14 dB SNR form my
INV-L antenna. I remember it took ~ 100 hours to wind that 6.1 H coil,
which had a relatively short life time and was quite expensive!
I already conclude: Ground loop antenna are doing a great job, not only
on ULF but also on VLF!
Will you continue to improve the H field? Same here, i need to work on
the H field. For the 470 Hz experiment and later at lower frequencies,
the distance is in the near field already and so i will need the H field
on the RX side.
I recorded the stream of DL4YHF and Renato/IK1QFK. From that data
storage i post-processed a spectrum peak on 8270 and 2970. It is
interesting to see the difference! Wolfgang is in 313 km distance
(http://k7fry.com/grid/?qth=JO42FD&from=JN39WI) and Renato is in 492 km
(http://k7fry.com/grid/?qth=jn34rw&from=JN39WI). On 8270 Hz they both
got a very strong signal. On 2970 Hz, Wolfgang got also a very strong
peak but Renato got nothing at all! Maybe another ground/skywave
cancellation? Results attached.
The propagation curves of this frequency range are quite dynamic for
distances below 1000 km. Maybe 2970 Is not ideal for distances for you
and Jacek. Eventually 2470 Hz or 1970 Hz is even better? At least the
good SNR at DL0AO and DL4YHF promises that the SNR will be high enough
on these lower frequencies to allow a comparison! So it is worth to TX
another 2 hours there. Also it would be a new record distance of > 1
lambda on these bands.
73, Stefan
Am 31.12.2018 00:40, schrieb Paul Nicholson:
Best I can manage here is 11.9 dB S/N in 139uHz from the 9nV/m
E-field signal. A little over 2 electrons on the antenna.
http://abelian.org/vlf/tmp/181230a.gif
The pipeline uses
vtfilter -h bp,f=2470,w=1600 -a th=5
and
vtblank -a25 -d0 -t100
which gives a drop factor of only 0.8%. With daytime sferics
at this frequency there is little for the blanker to blank. It is
mostly dropping mains-asynchronous switching pulses from the DC
supply.
E-field only reception for this.
The H-field rx is not working very well at this frequency, the
noise floor is a few dB higher. A combination, I think, of mains
sidebands and interference from the DC supply. Somewhere on my
workbench are the parts for a new 48V DC supply with much better
isolation.
I think this is actually a record distance for carrier detection
without stacking.
--
Paul Nicholson
--
8270 und 2970 Träger an Erdantenne.png
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