Paul,
If it's of interest, I'd hazard a guess that accommodation of > 8.3 kHz
amateur signals by lightning networks could ultimately yield a net benefit
to the lightning networks; I'd be happy to collaborate with any amateur
effort toward accommodation. State of art commercial lightning geolocation
employs enough discrimination* that weak narrowband amateur signals should
either be irrelevant or easily excised**. Lower cost (lower accuracy)
lightning geolocation networks are in some cases limited by propagation
models (and propagation data to develop such models), and these and more
sophisticated lightning geolocation networks might find value in amateur
resources applicable to propagation models.
*discrimination in multi-band spectrum, time, amplitude, mode and
polarization
** Given the spacing of even the most dense large-scale lightning
geolocation networks, the likelihood of separation of less than a few km
between intended amateur TX equipment and existing lightning geolocation RX
equipment should be very low, and exclusion of such cases probably
manageable.
On another topic derived from your message below:
Thank you for the information regarding Mike's receiver. I have operational
VLF TX equipment (broadband tunable, 3kW PA) in Arlington, VA, ~300km from
the vlf35 'Forest' location that you indicated. I have been hoping to
position (height, separation from infrastructure) and scale the antenna for
T/A but have run into time constraints trying to make far-field measurements
on my own. Measurements at ~ 300km would be very helpful for validating
height and separation constraints prior to scaling the antenna for
long-path. Do you think Mike would be interested?
73, Jim AA5BW
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Paul Nicholson
Sent: Monday, June 2, 2014 2:17 PM
To: [email protected]
Subject: Re: VLF: W4DEX trans-Atlantic at 8971 Hz
Going east to west is much harder, maybe 20dB harder, thanks to anisotropy
of ionospheric reflection which is very significant at VLF.
Mike Smith near Lynchburg, VA, has an excellent E-field rx at a quiet
location. I have hopes he will put up orthogonal loops.
Mike uses the same VLF software as used here,
http://abelian.org/vlfrx-tools/
Mike's VLF receiver is streamed online, see vlf35 'Forest' at
http://abelian.org/vlf
and there is a temporary 8971.1 Hz spectrum updated every 30 mins at
http://46.4.26.83/sp8971_vlf35.png
Uwe DJ8WX made determined attempts earlier in the year to reach Lynchburg
and I used every trick I could think of to search for his signal in Mike's
data, but I think we were still a few dB under the noise.
Stefan wrote:
> PS: 8.97 (+-), that was the _right_ frequency range *thumbs up*! :-)
Indeed, when operating at the limits of what is possible, the dB or
so difference between 8970 and 8270 becomes very significant. The
European restriction to sub 8.3kHz is presumably to avoid lightning
detection networks. But these would surely be unaffected by these very weak
amateur signals unless the tx was within a few km of
a meteorological receiver. Perhaps with suitable representation
from national amateur radio organisations, the situation could be
re-considered.
--
Paul Nicholson
--
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