5.17kHz loading coil

This was a photo from 5 years ago of the 5.17kHz loading coil at DF6NM. Some remarkable distances have been spanned by amateurs at these VLF frequencies. 

QRM on VLF?

DK7FC, PA3CPM and DF6NM have all been TXing today around 8.970kHz with reception reports coming in from many of the western European grabbers. DF6NM is running some 20dB less ERP than Stefan yet is appearing on UK grabbers quite well just HF of DK7FC. PA3CPM is a much weaker signal although he has been copied by Paul Nicholson in Todmorden UK. Activity is likely to continue over the weekend. Here is a screen grab from Eddie G3ZJO's VLF grabber today showing 2 of the active stations quite clearly. Notice the timescale on Eddie's grabber: between markers it is 4 hours in his DFCW6000 window, so don't expect snappy QSOs on VLF.

Busy amateur VLF weekend

G3ZJO's reception of DK7FC on 8.97kHz

Yesterday's test by DK7FC from his fixed location was a resounding success with reception all over Europe by many stations including G3ZJO, G3WCD and G3KEV, and what is believed to be the first transatlantic reception of an amateur VLF signal by a station in the Eastern USA. Results are being checked as I write.

Stefan's ERP was later re-calculated as around 800uW. It is incredible that such a tiny VLF signal can be detected so far away. If confirmed, this certainly heralds the dawn of a new and exciting phase of VLF amateur work. With another 3-6dB ERP, worldwide amateur VLF DX is now a real possibility. Of course such VLF DX reception requires incredible frequency stability, very narrow RX filters and long signal integration times; signals are far too weak to hear.

Also, Marcus DF6NM ran a 8.97kHz test today using a kite antenna. G3ZJO received a good signal in IO92ng 20dB above the noise in 424uHz bandwidth. Marcus was also well received by many other stations across Europe.

In summary, this weekend has been a BUSY one on the Dreamer's Band.

VLF kite transmission by DF6NM

DF6NM's signal in the UK

Marcus DF6NM carried out another successful VLF test yesterday on 8.97kHz (200uW ERP) and 6.47kHz (50uW ERP) with reception by Paul Nicolson in Todmorden UK.  Marcus is the second German VLF amateur to be copied at this distance.

German VLF earth mode test: 5.2 km on 8.97 kHz

Stefan DK7FC has been doing some experiments with around 50W to a 300m spaced grounded earth electrode "antenna"  in a remote location in Germany. Today his experiments were successful with his transmission of 30 minutes clearly received on his E-field probe receiver and grabber located in the city some 5.2km away.  See the report on his experiments at  http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF_5km_with_an_earth_antenna.pdf . Stefan can improve the electrode arrangement and increase current into the ground as well as run up to 500W. He's hoping to see the signal on the DF6NM VLF grabber located 174km away. If successful, this would be the first reported amateur radiated VLF DX using earth electrode antennas.

2-way QSO on the 8.97kHz "Dreamers Band"

DJ2LF and DF6NM held what was probably the first two-way contact on 8.97 kHz. The distance between them was 20.2 km, well outside the reactive near field zone (λ/2π = 5.3 km). In each case the radiated power was about 5uW. They used a special QSO procedure using dual frequencies. Congratulations to both stations.

DF6NM and DK7FC active on 8.97kHz today

Not one, but 2 stations were active on 8.97kHz today in DFCW mode. Part of DK7FC's transmission was copied at 902kms away in Warsaw and DF6NM, running a much smaller station and antenna, was copied 21kms away. A first QSO on the 33kms band cannot be too far away now!

8.97kHz VLF grabber on-line in Germany

DF6NM in Nuernberg, who has been successfully experimenting with sub-9kHz communications now has a temporary grabber on-air to capture any amateur signals on 8.97kHz.  See http://www.mydarc.de/df6nm/vlf/vlfgrabber.htm

New amateur DX record below 9kHz (VLF) - 12.1kms

Markus DF6NM has reported on the LF Reflector that he's been able to receive his test transmissions on 8.97kHz at a distance of 12.1kms. See http://www.mydarc.de/df6nm/vlf/vlf_12km.jpg. He has calculated his ERP at 1.3uW into his relatively small antenna with 1.4 Henry loading coil. The TX was a 35W car-radio audio amplifier. His RX antenna was 6m long and he used SpecLab with very narrow effective bandwidth. There are several others now experimenting below 9kHz, so this new record may not last long, especially as Marcus was using relatively low TX power. OFCOM is considering the issue of NoVs for <9kHz in the UK.