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Message-ID: <FE47E3F1638A4C34B221F5D8670639FB@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4FE39E8E.8000301@iup.uni-heidelberg.de> <41D4AB78ABB34782B413399ED4F3481A@gnat> <4FE3B641.2000709@iup.uni-heidelberg.de>
Date: Fri, 22 Jun 2012 01:47:29 +0100
MIME-Version: 1.0
Subject: Re: LF: Re: 15 dB noise drop in 20 minutes
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Hi Stephan, I dont know for certain. It is a long distance I would expect 
DCF39 to disappear after dawn......I wiuld expect a big drop from the 
darkness level maybe a return  weaker peak "blip" before complete loss an 
hour after local ground sunrise. If its still active listen for CFH Halfax 
NS on 137.00kHz. Its a mil data transmission. at about the same ERP
If the daytime tramsmission is "real DCF39" Its strength should increase 
from dawn until mid-day at mid path then deline slowly towards dusk. This is 
not great may only be 2-3dB but very consistent day to day and up to 6dB 
stronger in daytime during a magnetic storm (Kp=6) maybe 10dB during a 
severe event (Kp=9)** but I have no real knowledge of this so far towards 
the equator. All my data is from N. Europe

** the hot electrons that give absorption at night, help daytime skywave 
usually for just a couple  of days after an event (elevated Kp)

You should see the telegrams but I guess you are using to narrow a 
resolution. With reasonable frequncy calibration DCF39 should be within 
0.1Hz of what Markus measures. You may need GPS for this, I doubt WWVB will 
be accurate enough. at that distance.

Alan.
----- Original Message ----- 
From: "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
Cc: "YV7MAE Maritn A. Echazarreta D." <yv7mae@gmail.com>
Sent: Friday, June 22, 2012 1:03 AM
Subject: Re: LF: Re: 15 dB noise drop in 20 minutes


Alan,

What do you think about the remaining signal of DCF39 after the sunset?
Is it really DCF39? Or a local QRM line? I once took a recording and
reprocessed it here on my PC. I saw there is a local line (without the
data bursts) but it was some Hz below DCF. Since the receive system is
reasonable stable (drift < 0.1 Hz) i reduced the frequency range for
detecting the signal level for the DCF plot to a BW of 1 Hz. Anyway
there appears a trace which is > -30 dB below the night peak but anyway
visible. Realistic? That path is almost completely over water. In some
days you can even see the steps of S/N reduction due to the sunrise in
the reflection zones. At least it looks like that..

With a receive loop in winther i think even G3KEV has a chance to appear
there ;-) For winther i expect at least a 10 dB S/N improvement, maybe
rather 20 dB. A loop which cancels the noise from the southern
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 where 
> the interference originates. Because there is virtually no skywave 
> propagation in the "sunrise dip", no noise is propagated by skywave (> 
> 1000km) from the east. Where you live you have large cities all round you. 
> We get this effect on the edge of Europe as the daylight kills the 
> night-time propgation of noise fron the East (there 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 
> despite trying it didnt work out that way. Mike G3XDV and Brian CT1DRP 
> tried quite hard..... but eventually made the qso mid morning, when the 
> noise was up again due to increases in daytime skywave!! That is if I 
> remember correctly.....it fascinated me as I was just getting interested 
> in LF long distance propagation around then. We found evening effects in 
> Nova Scotia and I believe similar effects were reported by John W1TAG and 
> Jay W1VD who are very close to the US East Coast.
>
> Alan
> G3NYK
> ----- Original Message ----- From: "Stefan Schäfer" 
> <Stefan.Schaefer@iup.uni-heidelberg.de>
> To: <rsgb_lf_group@blacksheep.org>; "YV7MAE Maritn A. Echazarreta D." 
> <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 sunrise. 
>> On your grabber 
>> (http://dl.dropbox.com/u/74746618/LF/YV7MAE_LF_Grabber.html ), i can see 
>> the noise drops 15 dB within 20 minutes. That means the sun must be very 
>> strong so the ionosphere is very quickly ionized. Also the local 
>> lightning density must be extreme. All in all it looks like a 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 
>> minutes...
>>
>