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Re: VLF: Sunday morning test 8270.020 Hz

To: <[email protected]>, <[email protected]>
Subject: Re: VLF: Sunday morning test 8270.020 Hz
From: "Markus Vester" <[email protected]>
Date: Mon, 8 Apr 2013 00:18:48 +0200
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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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