Re: VLF: Back on 5.17 kHz / 58 km...

[Paul Nicholson <vlf0403@abelian.org>]

Stefan wrote (12th Jan):

> f = 5170.000000 Hz
> Start time: 13.Jan.2017 08:00:00 UTC  (daily repetition)
> Symbol period: 6 s
> Characters: 100 (!)
> CRC bits: 8
> Coding 8K19A
> Duration: 8h, 20m, 48s
> Antenna current: ~ 225 mA

Decoded via DL4YHF at Bielefeld (303.8 km):

 'VERY LONG MESSAGES CAN BE SENT BY RADIO AMATEURS ON VLF USING
  EBNAUT SOFTWARE. 73 DE DK7FC IN JN49IK'

Each day:

 2017-01-13   -7.9 dB   138.6 deg   S/N -59.1 dB
 2017-01-14   -4.5 dB   136.0 deg   S/N -55.7 dB
 2017-01-15  -28.4 dB   N/A         S/N -79.6 dB
 2017-01-16   -8.0 dB   138.7 deg   S/N -59.2 dB
 2017-01-17   -6.4 dB   144.9 deg   S/N -57.6 dB
 2017-01-18   -7.1 dB   146.1 deg   S/N -58.3 dB

5 days stacked (excluding 15th):

 Decoded with  0.2 dB   140.3 deg   S/N -51.0 dB

Some combinations of 4 days also decode at -0.4 dB.

At Todmorden (881.2km):

 2017-01-13  -11.1 dB   44.5 deg    S/N -62.2 dB
 2017-01-14  -12.1 dB   35.3 deg    S/N -63.3 dB
 2017-01-15  -37.0 dB   N/A         S/N -88.2 dB
 2017-01-16  -14.0 dB   22.3 deg    S/N -65.2 dB
 2017-01-17  -13.5 dB   26.6 deg    S/N -64.7 dB
 2017-01-18  -14.0 dB   41.6 deg    S/N -65.2 dB

5 days stacked (excluding 15th):

              -4.8 dB   36.7 deg    S/N -56.0 dB

Would probably need altogether at least 20 days to get
enough signal to decode at Todmorden.

> The todays [15th] transmission failed again for some reason
> :-( No idea what the reason could be.
> It stopped 15:46 UTC, about 3/4 hours to early.

From the S/N it looks like it had more effect, perhaps the
phase went wrong earlier in the transmission before it stopped.

--
Paul Nicholson
--