Hi Stefan,

strangely, nothing is visible here in Nürnberg now.

At DL0AO, the portable transmission (~ 280 km) appears to be around 9 dB stronger compared to the institute in Heidelberg (~ 230 km, reference measurement at 7:50 UT on Dec 27). However here in Nürnberg it seems to be the other way round: the transmission from the institute (180 km) was strong  (up to 20 dB SNR) all day, but the signal from the guiderails (230 km) is completely invisible now. 

The explanation may be that a sharp midday minimum exists at 230 km. Looking at DL0AO traces, we can see that the signal from the institute indeed almost disappeared at noon. During earlier Experiments it seemed that the minimum was very pronounced on our 180 km path, but that was later in the year around April and May. This seems to make sense, as higher solar Illumination pushed the midday ionoshere further dowen, requiring steeper skywave angle to arrive at the same 3/2 lambda path difference for cancellation. 

Best 73,
Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: DK7FC <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Sa, 29. Dez 2018 13:45
Betreff: LF: VLF Carrier on 8270.01 Hz from a ground loop antenna - The 6th station on Paul's spectrogram

Hi VLF friends,

Since 11:35 UTC i'm running about 2.5 A antenna current into my 900m
long ground loop antenna. Frequency is 8270.01 Hz. The signal is very
strong on my own grabber in 57.6 km distance but also at DF6NM, DL0AO
and it looks like there is a peak now on Paul's spectrogram building up
slowly.
I intend to run the carrier for 2 hours or so, until the accu is almost
empty :-)
The H bridge PA voltage is 175 V and the power consumption is 450 W.
Today, the DC measuremant result is 66V for 1 A antenna current. It is
cold and wet!
More soon.

73 de DK7FC/P in JN39WI

PS: The QRN is exceptional low!!!!