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.pdf
has 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.htm
Judging 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)
