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
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