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From: Stefan Schäfer <[email protected]>
To: Daniele Tincani <[email protected]>
Cc: Renato Romero <[email protected]>; Paul <[email protected]>; [email protected]
Sent: Mon, October 4, 2010 1:43:28 PM
Subject: VLF: VLF at different locations and QRN as a function of daytime

Hi Daniele, VLF,

Congrats to your successful VLF reception! :-) If you compare your received signal to that of Renato Romero, it is not much weaker. Since Renatos Antenna is excellent, i assume the low S/N is caused either by local QRN in Italy or simply by the propagation. If i remember correctly, in my 3rd experiment, Renatos reception was one of the best of all! So maybe we should/could learn something about the VLF propagation between Germany and Italy, above the alps. I think the lower S/N is not (only) due to the presence of the alps! All this is very interesting :-)

There is still no reception in Italy on 6470 Hz (46 km band), sadly. It is just because of my mistake with the generator :-( At least 2 hours of TX time was lost :-( Ok, never mind...
Maybe 6470 Hz is much more suitable to cross the alps. We will check this in the next experiment i would say? :-)

6470 Hz has many advantages i think, at least if the mains hum at a given RX location is about at equal or less strength than on 8970 Hz. I have observed that the (day)time of low QRN is much longer there. Another question is how the S/N as a function of time behaves. Attached you see a capture of my 'wideband' grabber window of the last sunday (including those nerving horizontal local QRM lines). You can see the frequency region of the maximum sferics level is changing with daytime. On 8970 Hz it is 'dark' from 7...12 UTC but on 6470 Hz it is 'dark' from 7...17 UTC.

Maybe some VLF receiving OMs can record their 'wideband' window on their own location and we can share the results. This makes it easyer the compare the situation of various locations :-) And we could discuss about the best time for a transmission either on 33 km or on 46 km to reach a given location.

Daniele, can you tell me your call and locator? I want to set up a list of the successful VLF receptions :-)

73, Stefan/DK7FC