Hi Roger,
Wish you good luck and fun with the experiments!
Who is the next possibe RX station and what is the distance? What is
his RX situation?
Maybe you can monitor your own generated TX signal on a high accuracy
soundcard based VLF RX to get some informations about its stability.
This would help you to find the slowest useful QRSS mode for this
setup/VFO.
Will you do some /p TX experiments? I mean, generating 4W (or 20 W) is
not a problem with a small lead acid battery and you could arrange a
secret earth antenna in the forest, some km away and some 100m long :-)
Do you plan to arrange a fixed VLF RX antenna to monitor the other NoV
holders? Maybe a first QSO in UK like between DF6NM and DJ2LF?
Interesting stuff!
73, Stefan/DK7FC
Am 03.11.2010 15:18, schrieb Roger Lapthorn:
This morning from 0915-1115 GMT I transmitted a QRSS3
beacon signal on 8.760kHz under the terms of my Dreamer's Band NoV
recently received. I think this may be a first in the UK, legally at
least.
TX was 4W from a TDA2002 audio IC matched into earth electrodes 20m
apart. The beacon message (callsign and QTH locator in QRSS3) was
provided by a K1EL keyer chip and the frequency reference was an HF
crystal divided down by 512 times in a 4060 divider IC. Clear QRSS3
reception was possible 5.1km away from the transmitter location
(see attached screen shot from Spectran), detecting the signal with an
80cm loop fed into an E-field probe (Hi-Z input) into Spectran
software. Marginal reception was just possible at 5.3km. Best reception
was always with the loop flat on the ground suggesting the main mode of
propagation is utilities assisted earth mode, as was the case at 838Hz
back in the summer.
Comparing results on 8.76kHz with those at 838Hz earlier in the summer
in several locations from 1.5km out to 5.4km, my first impressions are
that signal levels are at least 6dB weaker on 8.76kHz, but more careful
tests will be needed.
When I tried to look for any sign of radiated signals by aligning the
loop vertically end-on to the TX location, no signals were detected
although with QRSS3 and receiving in the bandwidth used this would have
been very optimistic with 4W from the transmitter into earth electrodes.
In the next couple of days I want to try the same set of tests using
the 70m square vertical TX loop used on 500kHz and 136kHz. If my theory
is correct and this is utilities assisted earth mode then I would
expect results to be far worse with the loop as there will be less
strong coupling into the ground.
At some point in the near future I will do some extremely slow QRSS
tests and let people know beforehand when the transmissions will take
place. There is some remote chance that slightly more distant stations
may be able to detect the signal although I have not been able to
measure my frequency with the precision really needed yet.
As I said some days ago, these tests are not at all in the same class
as Stefan's experiments, but they are fun to do and I'm learning all
the time.
UK dreaming has started, if only modestly.
73s
Roger G3XBM
--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM GQRP 1678 ISWL G11088
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