Dear VLF,
The recent discussion about the optimal frequency and propagation on a
given RX/TX distance is an interesting issue. Furthermore Markus/DF6NM
and Paul Nicholson has demonstrated that it is possible to detect a 5
uW EMRP signal in > 1000 km if the integration times are very long
(>5 hours) and the carrier is (VERY) stable in frequency.
Since my earth antenna, currently 600m spaced earth electrodes and
about 700 Ohm overall losses, seems to have a not too bad efficiency
(remembering my 250 W DFCW-600 transmission was undoubly copied by
Michael Oexner in 49.6 km on 8970 Hz) it could be possible to receive a
long time transmission, GPS locked, in a very small FFT too. The
advantage is that this antenna has not to be resonated and covers the
whole VLF/LF spectrum with "suitable" efficiency. Thus it will be
possible to try different TX frequencies and one can see if there are
optimal frequencies for different locations, knowing that the antennas
efficiency is a function of the frequency.
Thus i want to do a VLF 24 hour non stop transmission, starting on
8970.00500 Hz. I have got some big lead acid car batteries (12 V /
300 Ah in sum). First i want to try my small PA (300W) running at about
100 watts. For that, i will leave the car into the forest, over the
night.
I am still not sure if my GPS receiver is working in the forest but we
will see.
Note that this test cannot be compared to a kite antenna experiment.
The signal is probably 30 dB weaker! Anyway it is worth a try, with
longer transmission- and integrating times. Additionally the antenna
may have some directivity. This would be interesting to be confirmed.
S/N oriented stations may be preferred but everyone is invited to try
to receive something :-)
If some RX stations would receive this very weak signal, they will be
able to provide informations at which time the signal level was
strongest and when the S/N was best.
Attached you find a SpecLab usr file with probably useful settings. I
have choosen a FFT of 141 uHz (width of one FFT bin). If you want you
can use this for reception.
Please let me know if you are interested to participate in this test.
It shall start in the late afternoon of wednesday, 10th November.
The exact starting time is not sure since i have to be at work in the
morning. Furthermore i want to reduce the earth rod losses even more by
applying another 20 rods what will take some time. The experiment has
to be during the week since on the weekend, to many people are crossing
the way there...
73, Stefan/DK7FC
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24hExperiment on 8970 in 141uHz.USR
Description: Text document
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