Message-ID: <4FE3B641.2000709@iup.uni-heidelberg.de>
Date: Fri, 22 Jun 2012 02:03:13 +0200
From: =?ISO-8859-15?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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CC: "YV7MAE Maritn A. Echazarreta D." <yv7mae@gmail.com>
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Subject: Re: LF: Re: 15 dB noise drop in 20 minutes
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Alan,

What do you think about the remaining signal of DCF39 after the sunset?=20
Is it really DCF39? Or a local QRM line? I once took a recording and=20
reprocessed it here on my PC. I saw there is a local line (without the=20
data bursts) but it was some Hz below DCF. Since the receive system is=20
reasonable stable (drift < 0.1 Hz) i reduced the frequency range for=20
detecting the signal level for the DCF plot to a BW of 1 Hz. Anyway=20
there appears a trace which is > -30 dB below the night peak but anyway=20
visible. Realistic? That path is almost completely over water. In some=20
days you can even see the steps of S/N reduction due to the sunrise in=20
the reflection zones. At least it looks like that..

With a receive loop in winther i think even G3KEV has a chance to appear=20
there ;-) For winther i expect at least a 10 dB S/N improvement, maybe=20
rather 20 dB. A loop which cancels the noise from the southern=20
hemisphere, many stations will have good chances to appear in SA i think.

73, Stefan


Am 22.06.2012 01:46, schrieb Alan Melia:
> Hi Stefan, this is a function of propagation, I think. It depends on=20
> where the interference originates. Because there is virtually no=20
> skywave propagation in the "sunrise dip", no noise is propagated by=20
> skywave (> 1000km) from the east. Where you live you have large cities=20
> all round you. We get this effect on the edge of Europe as the=20
> daylight kills the night-time propgation of noise fron the East (there=20
> a few big cities or industrial noise sources for 3000 km W of Ireland
> :-))  )
>
> It was thought at first that this would be the best time for DX, but=20
> despite trying it didnt work out that way. Mike G3XDV and Brian CT1DRP=20
> tried quite hard..... but eventually made the qso mid morning, when=20
> the noise was up again due to increases in daytime skywave!! That is=20
> if I remember correctly.....it fascinated me as I was just getting=20
> interested in LF long distance propagation around then. We found=20
> evening effects in Nova Scotia and I believe similar effects were=20
> reported by John W1TAG and  Jay W1VD who are very close to the US East=20
> Coast.
>
> Alan
> G3NYK
> ----- Original Message ----- From: "Stefan Sch=E4fer"=20
> <Stefan.Schaefer@iup.uni-heidelberg.de>
> To: <rsgb_lf_group@blacksheep.org>; "YV7MAE Maritn A. Echazarreta D."=20
> <yv7mae@gmail.com>
> Sent: Thursday, June 21, 2012 11:22 PM
> Subject: LF: 15 dB noise drop in 20 minutes
>
>
>> Hello Martin, LF,
>>
>> I'm fascinated by the noise drop on LF which occurs during your=20
>> sunrise. On your grabber=20
>> (http://dl.dropbox.com/u/74746618/LF/YV7MAE_LF_Grabber.html ), i can=20
>> see the noise drops 15 dB within 20 minutes. That means the sun must=20
>> be very strong so the ionosphere is very quickly ionized. Also the=20
>> local lightning density must be extreme. All in all it looks like a=20
>> very sensitive system. But some directivity would be interesting :-)
>>
>> 73, Stefan/DK7FC
>>
>> PS: I will be on 136.172 kHz again this night, starting in a few=20
>> minutes...
>>
>