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Peter,
LF,
daytime VLF propagation normally
depends on distance, solar elevation at midpath, and frequency. I
noticed that Uwe and Henny are both around 180 km from you. This happens
to be roughly the same distance as between Stefan and
myself, where we used to find a pronounced midday
minimum on 8.97 kHz. Ossi (200 km southeast) and I had the same
effect. On the other hand, the ~ 400 km path to OE3GHB and OK2BVG was
usually stronger during the day.
The distance between Appingedam and Nuernberg is
525 km, and I'm really not sure if there
would be margin for a significant nighttime enhancement between
us. Keep in mind that Uwe is not only much closer to you, but his
ERP is probably an order of magnitude larger than mine.
I have uploaded some screenshots from today to http://df6nm.bplaced.net/VLF/8k27 .
Paul's spectrogram clearly shows that my
frequency was below nominal between 10 and 11 UT. This is
corroberated by the Loran moire pattern, and also by a trace which
happened to be created by harmonic mixing in the high resolution
Opera-deep-search spectrogram. To trace down the problem I plotted the
samplerate deviation history from the VLF transmit samplerate detector. It was
tracking DHO 23.4 kHz with SpecLab's default settings (10 s update cycle which
is actually 1 / 0.072 Hz, 1 ppm maximum deviation). The samplerate was generally
very close, but there appeared a number of discrete +- 0.76 ppm
excursions, possibly due to discontinuities in the ADC data stream. After
9:50 these spikes became much more frequent and apparently pulled up the average
samplerate measurement result, producing a -0.3 mHz error
in the transmit frequency. Around 11 UT I noticed that something was wrong,
and increased the measurement interval setting to 20s (1 / 0.036 Hz), which
smoothed the data and apparently eliminated the spikes. I also reduced
the confidence interval to +-0.1 ppm. Thereafter, the rest of the
transmission from 11 to 13:45 was flawless.
Best 73,
Markus (DF6NM in JN59NJ)
Sent: Sunday, April 07, 2013 8:19
PM
Subject: Re: VLF: Sunday morning test
8270.020 Hz
Hi Markus,
Unfortunately you where already QRT
befor the propagation got better. You'r right, perhaps propagation to
your direction is differend in relation between Uwe and my QTH.
If you take a look (in my grabber) at DJ8WX
his signal and you's, there is not much difference.
Uwe is already running for such a long time,
he leaves a impressive trace, but between 8 and 13 is his signal also weak
at my QTH.
Perhaps it is possible for you to switch on a
few hour between sunset and sunrise !
Best 73's, Peter.
----- Original Message -----
Sent: Sunday, April 07, 2013 12:35
PM
Subject: Re: VLF: Sunday morning
test 8270.020 Hz
Peter,
yes I was also wondering whether it
was really me but now it's sure. I think I did have some samplerate
tracking issues around 11 UT, but it looks good again now. Interestingly but
perhaps unrelated, DHO went off air for a minute at
11:18.
In the past we have observed that the
diurnal propagatipon pattern depends on the phase between groundwave and
ionospheric components, and thus on the distance between TX and RX. So it may
well be different between you and Uwe, versus you and myself. Unfortunately I
won't be able to transmit contiuously throughout day and night, and
will have to go off air around 13 UT today.
Best 73, and thanks again,
Markus (DF6NM)
Sent: Sunday, April 07, 2013
2:13 PM
Subject: Re: VLF: Sunday
morning test 8270.020 Hz
Hello Markus,
VLF
At first I was quite sure, but later in the morning I started to doubt whether I did receive DF6NM.
Meanwhile, in the afternoon I really see the trail of DF6NM appear in the spectrogram.
As you can see in the traces
of DJ8WX (in my grabber) the propagation is not good during daylight
between us.
I hope you are able to stay
on air for a while.
73s
Peter
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