Sorry, first
email was corrupted because I had forgotten to fill in the subject line. 73,
Markus
Dear Sub-9kHz'ers,
Marco DD7PC
just made me aware of new German regulations, which also includes a change of
the unallocated VLF range. The latest version of the "Freqenzverordnung"
(FreqV)
http://www.gesetze-im-internet.de/bundesrecht/freqv/gesamt.pdfhas
become effective already on August 27, 2013, and includes an allocation of 8.3
to 9 kHz to the passive weather observing service (ie. lightning locator
networks). Strictly speaking, this would make 8.97 kHz transmissions illegal
in Germany (although there may be a loophole with national footnote 2
regarding "Induktionsfunkanlagen"). If I recall right, a similar legal change
in the UK had been announced in this group some time ago, leading to the
installation of some grabber windows around 8.27 kHz.
In practice,
radiated powers achievable by amateurs (milliwatts at best) are ten orders of
magnitudes below to that emitted by lightning events (100 megawatts). The
chance of amateur interference to a broadband lightning locator would thus be
absolutely neglegible. Even if somebody happened to activate his kite within
one kilometer from a detector station, any further effect of interference
would still be suppressed by redundancy in the lightning location network.
Still, for
publicly visible work (like claiming first contacts etc), we should consider
moving below 8.3 kHz. Of course there are disadvantages, like
- local
interference eg. from railway lines seems to be much denser and stronger at
lower frequency,
- at same antenna voltage, radiated power will be 1.4 dB
less,
- more coil winding is required,
- acoustical side-effect of
transmitting may be more disturbing,
... es nervt einfach!!
But then, one
should always embrace change... positive aspects may be
- lower QRN
background in quiet locations,
- with common international legislation, the
necessity of sub-9kHz NOV's in the UK might become obsolescent,
- EA5HVK
might be motivated to provide an Opera version with flexible frequency
assignment.
In my location,
I am mostly affected by 16.67 / 33.3 Hz modulated interference emitted by
railway overhead lines, in addition to the usual 50 Hz related junk. To
possibly identify a sweet spot with relatively low interference, I have
temporarily shifted the frequency range of my faster VLF grabber
windows:
http://df6nm.darc.de/vlf/vlfgrabber.htmJudging by the
first hours, near 8280 Hz may be significantly better than 8270. But
interference comes and goes with time, so longer observations are needed. Note
that the heavy interference between 11 and 12 UT could have been exacerbated
by my noise blanker settings as it is much less severe in the wideband window.
At this time, I would like to encourage other receiver operators to closely
investigate their noise levels just below 8.3 kHz.
Best
73,
Markus (DF6NM)
