8.970 kHz - DK7FC's latest tests

Roger G3XBM reports that he was able to receive the latest VLF transmissions by DK7FC on 8.970kHz at a distance of 669km, the signal was also received by 4X1RF in Israel at 2873km !

Roger G3XBM writes:

This lunchtime [Saturday, Dec 5] I managed to copy DK7FC's latest test transmission on 8.970kHz at a distance of 669km. Reception was on my 20m spaced earth electrode antenna (!) into a small FET tuned preamp and Spectrum Lab software.

The signal was weak but correlates well with the signals also received by others across Europe and, amazingly, by 4X1RF in Israel.

My received signals are visible (live) on my VLF grabber at
https://dl.dropbox.com/u/15047843/xbm_grab.jpg .

If you look around 8970Hz you can see the signal as lines between about 1200 and 1400z. Notice the resolution needed to see this: it is also necessary to lock the sound card to a VLF MSK transmission to ensure frequency accuracy.

Although Stefan's ERP is QRP (<100mW) his input was around 500-600W to a 300m high kite supported Marconi vertical. Nonetheless, the latest tests confirm that some remarkable DX is possible and it is only a matter of time before the first amateur transatlantic VLF reports are received.

This is indeed a whole new frontier for amateur radio. I'm  pleased when my own 8.76kHz signal is copied just 5km away!

Update on reception in Israel:

On Dec 4 DK7FC's 100mW ERP VLF signal was copied and recorded by 4X1RF at an astounding distance of 2873km.

Signal levels suggest that transatlantic amateur VLF reception may indeed be possible in the near future. Several other stations across Europe (4X counts as Asia!) also copied Stefan's signals.

Extremely accurate frequency setting, very narrow bandwidth FFT based receivers and extremely long transmission times are all required to copy these signals at any DX distance - a casual listen on VLF would result in lots of noise and disappointment - but with some effort almost anyone with a small E-field probe or loop and a PC running freely available software can detect these signals.

To generate a signal that radiates more than a few uW on VLF is another matter and requires high TX power plus a kite or balloon supported antenna: efficiencies at VLF are extremely poor.

73
Roger G3XBM

G3XBM Videos
http://www.youtube.com/user/G3XBM

G3XBM Blog
http://g3xbm-qrp.blogspot.com/

G3XBM QRP Website
http://www.g3xbm.co.uk/

9 kHz Receiving Equipment
http://www.southgatearc.org/news/march2010/
9khz_receiving_equipment.htm

UK NoV's for Amateur Radio operation below 9 kHz
http://www.southgatearc.org/news/february2010/
9khz_nov.htm

G3XBM gets 8.97 kHz transmitter permit
http://www.southgatearc.org/news/october2010/
g3xbm_transmitter_permit.htm

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