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)
