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Re: VLF: 8.275 kHz

To: <[email protected]>
Subject: Re: VLF: 8.275 kHz
From: "Markus Vester" <[email protected]>
Date: Fri, 3 Jan 2014 12:10:11 +0100
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Peter, ok. But I still have a problem with the railway QRM on 8270, so I'd prefer either 8275 or 8280...
 
What do the others think? Chris, Eddie, Gerhard, Haldór, Jim, Laurence, Lubos, Paul, Stefan ?
 
73, Markus
 
 

Sent: Friday, January 03, 2014 11:56 AM
Subject: LF: Re: 8.275 kHz

Oops.. forgot to tell, but that 8270 Hz is a local experiment here.
Its a notebook PC at a wire here in my home.
No problem with 8270 here.
 
 
 
----- Original Message -----
Sent: Friday, January 03, 2014 10:43 AM
Subject: VLF: 8.275 kHz

Hi Uwe,
 
ok, but could you make that 8275 Hz?
 
PA1SDB seems to be bothered by a continuous line on 8270 and some noise on 8280. I also have significantly more QRM around 8270. 
 
8275 Hz is clearer, and I will retune my "6000" and "50000" grabbers there, along with the attached opds-4H and -32 postprocessing.
 
Hope that Lubos could also shift his lowest panel from 8270 to 8275 Hz.
 
Good luck,
73, Markus

Sent: Friday, January 03, 2014 11:10 AM
Subject: Re: LF: Re: 8.3 kHz

OK, Peter and all,
today Ill adjust the aerial system at 8270Hz. afterwards doing som e tests in modes carrier only and Op-4H.
GL
Uwe/dj8wx

Von: [email protected]
Gesendet: 02.01.2014 23:09
An: [email protected]
Betreff: LF: Re: 8.3 kHz


My grabber at 8270 is loading. Lets see what QRM does here between 8234 and 8305 Hz
 
(did just start it at 23h00)
 
 
 
 
----- Original Message -----
Sent: Thursday, January 02, 2014 1:12 PM
Subject: VLF: 8.3 kHz

Sorry, first email was corrupted because I had forgotten to fill in the subject line. 73, Markus


-----Ursprüngliche Mitteilung-----
Von: Markus Vester <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Do, 2 Jan 2014 2:07 pm

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)

 
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