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Ham Radio below 9 kHz

German Licensing Authorities issued license for 8.9 to 9 kHz!

(click on license to see details, approx. 200 kB each page)

After Walter, DJ2LF and Markus, DF6NM started with some very low frequency tests recently, three of us have asked the German RegTP for a special license to use the range between 8.9 to 9 kHz for scientific studies. The licenses were granted recently, valid for two years. We are allowed to run a transmitter output of 20 Watt and any modulation up to a bandwidth of 100 Hz.

I am currently testing an old 20 Watt music PA with two EL84 and have started to experiment with 100 pieces ferrite bars and 300m Litz wire to achieve the necessary 1/2 Henry (!) coil to get my 18m vertical LF antenna tuned up to the 35 km wavelength!

We do not expect much DX from this band, however, tests perfomed in the US on 3.5 kHz (see http://home.pon.net/785/EQUIP/transmit2.html) and  in the UK by late John, G0AKN (sk) (http://www.wireless.freeserve.co.uk/) have revealed that a couple of miles can be reached. G0AKN holds the record with 6.6 miles on 6 kHz. Christer, SM6PXJ also has a special license (7.0 to 8.5 kHz). My personal goal for the beginning is to span 5 km.

Current Achievements on VLF

Output Power
Antenna System
Maximum Distance 
G0AKN (sk)
6000 Hz
1 kW
ground electrodes
10.0 km (ODX, shared with KD4RLD)
600 Hz - 5000 Hz
100 W
3.3 km
8950 Hz
6 W
ground electrodes
1.3 km
8950 Hz
14 W
2.5 km
8930 Hz
10 W
1.0 km
10000 Hz
4 W
 ground electrodes (commercial equipment build to search underground cables)
3.0 km 
8969 Hz
20 W
4.5 km
8975 Hz
380 W
ground electrodes
1.6 km
8800 Hz
7000 Hz
6000 Hz
100 W
ground electrodes/loop
10.0 km (ODX, shared with G0AKN (sk)), signal was copied by W4DEX, see picture below
8900 Hz
8 W
0.1 km

The first two-way QSO between DF6NM and DJ2LF on 8950 Hz was conducted August 19, 2000 over a distance of 200m ("... can you hear me?"  "NO" - "can you see me?" "YES": that's amateur radio on VLF ...) using earth electrodes on both sides.

Markus, DF6NM describes his VLF transmitting experiments
Read some theoretical background about the radiation of earth electrodes
Dex, W4DEX describes the equipment used in the VLF experiments with KD4RLD

Some information about my VLF Transmitter

DL5KZ informed me about the ability to use equipment that is used to search for underground cables for our experiments. I got hold of a "RFT Trassensuchgenerator 81027" (available from Rainer-Förtig for 100.- DM).

This unit originally contains a 10 Watt transmitter for 1030 Hz and 10 kHz and a matching unit for a resistance between 0.7 and 2200 Ohm. I changed the frequency of the oscillator to 8930 Hz and used a u-shaped ferrite core (special thanks to DF6NM) to build a transformer/antenna coil with an inductivity of approximately 0.6 Henry. I get an antenna current of up to 130 mA into my 18m high unmrella antenna. This leads to the conclusion that the loss resistance is in the range of 1500 Ohm (compared to 60 Ohm on 136 kHz). I have calculated that the effective radioated power (ERP) is in the magnitude of 1 MicroWatt!

With a Datong converter, an FT-817 and a very short whip antenna (about 3m long) I was able to hear my signal in a distance of 1000m.

Next step will be to use this transmitter in the originally designed mode using ground electrodes.

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