Hi Roger,
Thanks for the flowers.
Your list sounds good/interesting/promising, useful steps! If you need
any help or have questions, just ask.
BTW, a really "useful result" is/was (for me personally) beeing visible
by an other RX station. And i think that you will be successful, faster
than you think! Getting an ultra stable RX is not the problem, getting
an ultra stable TX just a litte more effort. It will be essential in
all the tests outside the far field. The great advantage is that your
system is not /p, so it doesn't (almost) matter if you have to choose
QRSS-3 or QRSS-3000, since you have the time :-)
Maybe you want to check how a vertical antenna acts, driven with a LOPT
transformer (without the HV cascade on the output of course). This will
work at QRP levels and you don't need to resonate this antenna
(although this would be an advantage). If you can use a 10m high
vertical, i assume this will give the highest ERP(as long as the
vertical isn't hidden in a tree ;-) ), maybe the 100m earth antenna as
an alternative :-)
I become interested to try this (once more) since my grabber was
improved since the last test and the QRN is reasonably lower. I can
start with this tomorrow. My distance (now, at home) to the grabber is
just 1 km. :-)
Tell me if you need a test signal to check your RX performance :-)
73, Stefan/DK7FC
Am 03.11.2010 23:18, schrieb Roger Lapthorn:
Hi Stefan,
G6ALB is 3km away and he is hoping to copy my signal on 8.76kHz in the
near future. This should be possible with a stable signal, accurate
frequency setting, a bit more power and slow QRSS. My DX today was much
further than his QTH but I could not reach his QTH on 838Hz in a quick
test in QRSS3 back in the summer. We will be able to have a cross-band
QSO, albeit slowly when we succeed.
The list of things to do on VLF are:
- Sort out Spectrum Lab so I can know exactly where I am
transmitting and receiving (just a matter of familiarisation).
- Try the vertical loop antenna on TX and compare results locally
- Try ground electrode antennas at the RX end
- Try elevating the horizontal loop slightly above ground (this
is a suggestion from my NoV contact at the Met Office based on some
research with Omega beacon reception)
- Increasing the TX power to around 100W
- Increasing the earth electrode spacing (I can run out a 100m
long baseline in the fields behind my house for short periods)
- Optimising further the RX hardware (loop, E-field probe and
preamp)
- Receive a signal from you when all is optimised!
- Receive a signal from G3XIZ and G7NKS on the Dreamers Band
- etc, etc....
Next week is not possible as it is our grandson's 3rd birthday and he
is coming here with his French grandparents, mum and dad, so ham radio
is out but it will be a lovely occasion.
Basically I still feel I am "dabbling at the edges" of good Dreamer's
Band techniques whereas as you and other real experts (yes I mean this)
are doing the work professionally. My task is to learn from you and
others and gradually improve my capability on VLF to the point where
useful results can be achieved.
73s
Roger G3XBM
2010/11/3 Stefan Schäfer <[email protected]>
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
--
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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