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" <[email protected]>
To: <[email protected]>
Cc: "YV7MAE Maritn A. Echazarreta D." <[email protected]>
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"
<[email protected]>
To: <[email protected]>; "YV7MAE Maritn A. Echazarreta D."
<[email protected]>
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...
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