From: "Mike Dennison" <mike.dennison@ntlworld.com>
To: rsgb_lf_group@blacksheep.org
Date: Wed, 04 Oct 2017 10:59:37 +0100
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References: <15ec7c794b3-bff-66@webjas-vac136.srv.aolmail.net>, <alpine.DEB.2.11.1710022138560.734@mailn.lipkowski.org>, <59D2BD65.4080909@posteo.de>
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Subject: Re: VLF: 300 mA on 6470 Hz
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Unfortunately, nothing at all seen here on 6470Hz. Using the same 
system as on 8270, but with filter frequency changed, so should be 
OK. I am not using any preamplification here, just the LF antenna 
straight into the sound card (with a little filtering to get rid of 
hum and HF), so maybe the antenna is less efficient at this 
frequency. Will investigate further.

Mike, G3XDV
==========
 
> Hi VLF,
> 
> Since 22 UTC, a carrier with 300 mA antenna current is running at
> 6470.005 Hz. The ERP is about 50 uW. That's the next step in the
> series of experiments transmitting on frequencies down to DC :-)
> 
> The coil has 3 and 1/2 stacked buckets now. That gives about 1.3 H. It
> was necessary to separate the upper and lower two buckets a bit more
> than usually, otherwise the frequency was at 6223 Hz. I expect i will
> reach 5170 Hz when the spacing is reduced to the normal value (70 mm)
> and when i fully wind the upper bucket.
> 
> Here's an image of the construction as it was used on 8270 Hz: 
> http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/8270_new_coil.jpg
> The new construction uses one more of these buckets. They say there
> will be strong rain during the whole night. I don't yet know how this
> will detune the antenna. Maybe the safety circuit tripps. But if not,
> i intend to run the carrier for 24+ hours, so people can check their
> grabbers and phase and so on :-) A first EbNaut message will follow
> during the week...
> 
> 73, Stefan
> 
> 
> Am 02.10.2017 22:02, schrieb Jacek Lipkowski:
> > Stefan, thanks for the carrier, this helped me improve my grabber a
> > bit.
> >
> > i've changed the time range in my grabber to 7 days, so that you can
> > compare with your previous carrier, and also added a "normalised"
> > spectrogram:
> >
> > https://klubnl.pl/wpr/en/index.php/klubnl-pl-grabbers/grabber-4-8270
> > hz/
> >
> > in the normalised spectrogram the average of relative powers for
> > each timeperiod are normalised to a constant value. so this is
> > something similar to AGC, taking care of day/night noise variations.
> > i think Paul does something similat, because his spectrogram doesn't
> > show differences in day/night noisefloor.
> >
> > the S/N isn't great, but this is from a simple e-field antenna in
> > the middle of the city.
> >
> > i've also added a 6470Hz grabber for your next tests (and will add
> > 5170Hz and normalized graphs in the future):
> >
> > https://klubnl.pl/wpr/en/index.php/klubnl-pl-grabbers/grabber-sq5bpf
> > -6470hz/ 
> >
> >
> > VY 73
> >
> > Jacek / SQ5BPF 
> 
> 
> ---
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