Re: VLF: W4DEX in Europe at 8820 Hz

[Markus Vester <markusvester@aol.com>]

Paul,

 

once more, very impressive work! I'm tempted to call that a TA first for Dex and Wolf, and Renato at even larger distance is getting very close. But most of all, I think it's the cooperative effort between you guys which really deserves congratulations!

 

Markus (DF6NM)

 

Von: Paul Nicholson <vlf0403@abelian.org>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Cc: wolf_dl4yhf <dl4yhf@freenet.de>
Verschickt: Di, 2 Dez 2014 5:47 pm
Betreff: Re: VLF: W4DEX in Europe at 8820 Hz

 

Another plot from Wolf's receiver at Bielefeld, 

 

  http://abelian.org/vlf/tmp/141202e.gif 

 

This covers the full transmission from 22:30 UT in 50.5 uHz 

bandwidth.   The line at 8820.0000 is 11.7 dB above the 

noise in this 1980 bin span. 

 

It is the strongest bin in +/- 0.5Hz (19800 bins). 

 

Of course, I also checked nearby integer frequencies - when using 

PPS GPS timing there is the possibility of weak harmonics from 

the timing system. 

 

I tried Cumiana with this narrower bandwidth but no improvement. 

 

-- 

Paul Nicholson 

-- 

 

-----Ursprüngliche Mitteilung----- 
Von: Paul Nicholson <vlf0403@abelian.org>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Cc: wolf_dl4yhf <dl4yhf@freenet.de>; Renato Romero <contact@vlf.it>; Michael Smith <mike@unixnut.net>
Verschickt: Di, 2 Dez 2014 2:09 pm
Betreff: VLF: W4DEX in Europe at 8820 Hz

Spectrogram of W4DEX at Forest, VA (range 254km) 

 

  http://abelian.org/vlf/tmp/141202a.png 

 

No sign of any frequency lock problems now.   All the energy 

is concentrated in one frequency bin so the signal appears a 

lot stronger than the previous day. 

 

Unfortunately the rx at Hawley TX stopped sending its VLF 

stream yesterday. 

 

W4DEX was quite good strength at Todmorden, getting up to around 

0.15 fT which is slightly above LWPC prediction for 150uW ERP. 

Actually that's a very good signal - European TXs are often 

similar or less strength. 

 

Spectrum plot, average 00:00 to 04:00 UT combining E and H 

 

  http://abelian.org/vlf/tmp/141202b.gif 

 

The above is on the optimum bearing of 310 deg (line of sight 

is 285 deg). 

 

Average signal strength 0.12 fT, 13.9 db S/N in 69.4uHz. 

 

E-field S/N is 13.0 dB S/N and combined gives 16.49 dB S/N. 

 

The noise from the south west was fairly high until 02:00 so 

it wasn't really a good night for reception.  It would probably 

not have been successful to try a long BPSK message. 

 

We also see a low significance peak in the spectrum at 

Bielefeld Germany (52.146N,8.458E 6918km) in the same period 

and bandwidth: 

 

  http://abelian.org/vlf/tmp/141202c.gif 

 

8820.0000 at 10.0dB S/N is the strongest peak in +/-1440 

bins but there are noise peaks not much lower.  Widening the 

range to +/- 0.25 Hz (7200 bins) produces one stronger peak 

at another frequency. 

 

I suspect Wolf's receiver is picking up the signal but it is 

a dB or so too low to be claimed as a detection.  This is an 

E-field rx so there is no directivity to exploit. 

 

Cumiana, Italy (44.96N,7.42E 7173km) also shows an insignificant 

line at 8820.0000 with 8.8 dB S/N but there are nine stronger 

noise peaks in 2880 neighbour bins. 

 

Coherently combining Bielefeld and Cumiana produces a signal 

with 11.7 dB S/N 

 

  http://abelian.org/vlf/tmp/141202d.gif 

 

and this is the strongest signal in 23000 adjacent frequency 

bins (I didn't look any wider than that +/- 0.8 Hz range 

because there are some strong interference lines). 

 

It therefore looks like that Dex is getting into Germany and 

Italy but it needs a more significant result - without the 

devious trickery that I use to combine receiver outputs. 

 

If there was 50% or so extra antenna current and a good low 

background night, the extra 3 dB or so would surely put this in 

the bag. 

 

-- 

Paul Nicholson 

--