Re: LF: UK Dreamer's Band first transmission (8.760kHz)

[Roger Lapthorn <rogerlapthorn@gmail.com>]

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 <Stefan.Schaefer@iup.uni-heidelberg.de>

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


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