From: "jannsen" <0482183881-0001@t-online.de>
To: rsgb_lf_group@blacksheep.org
References: <5.1.0.14.0.20030327110712.00a9e3d8@gemini.herts.ac.uk>
MIME-Version: 1.0
Date: Fri, 28 Mar 2003 00:30:39 +0100
Message-ID: <18ygpT-1NrvtYC@fwd06.sul.t-online.com>
Subject: Re: LF: Unusual QRN
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
Sender: <owner-rsgb_lf_group@blacksheep.org>
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org

James Moritz schrieb:
> Dear Markus, LF Group
>
> At 16:47 26/03/2003 -0500, you wrote:
> >tonight the band seems to be plagued by a high level of background QRN. 
> >Not the usual  distinct static crashes, but rather a continous static 
> >crackling reminiscent of old 78-rpm shellack records. This type of noise 
> >has been present during some nights, but not often. Its southerly angle of 
> >arrival went along well with the usual explanation of very distant 
> >lightning activity.
>
> I have noticed similar noise on the band here also during the past few days 
> - the background band noise seems to be ~10dB over the usual levels, 
> swamping the Loran chatter that normally sets the noise floor, but can 
> "switch" on and off over a period of a few minutes. It seems to occur 
> during both the day and night time. I have been trying to record 
> spectrograms of it; unfortunately, some local mains noise sources also 
> produce a similar effect on the spectrogram, so it is difficult to tell 
> which is local and which is distant, unless you are actually listening to 
> the RX audio.
>
> I am slightly relieved it appears to be a distant natural phenomenon, 
> rather than yet another local noise source - hopefully it is not permanent! 
> Can anyone else hear it too?
>
> Cheers, Jim Moritz,
> 73 de M0BMU
>
>
Hi Jim, Claudio and Markus es Group,

yes, here in jo43sv the same noise - I compared it to Markus`s .wav file -
and the switch off time was abt 1730 UT if I remember right. a 
surprising situation: no LORAN-C lines to be heard or seen.

the noise of frequency hopping spread spectrum emissions Claudio mentioned
is different from the noise under discussion; the audible pitch is somewhat
higher; but maybe on LF they tune the channel switching time down.
usually on SW those emissions are some minutes on the air (protection against
direction finding); not for several hours like the noise we did observe on LF.

regards
Uwe/dj8wx