VLF earth mode

Many years ago I did quite a bit of experimenting below 10kHz. This was reception of G6ALB at 3km on 8.97kHz. I think he was running about 40W. This was 2011.

See https://sites.google.com/site/sub9khz/vlf-using-earth-mode.

Sub 10kHz amateur DX in 2011

Back in 2011 I was very involved in amateur VLF below 10kHz.  

To be successful bandwidths of tiny fractions of a Hz are needed and integration periods of hours or even days.  As would be expected stability has to be perfect with many locking their signals to GPS or similar. 

Remember, amateurs have limited power and space for antennas!

DJ8WX was a regular signal back in 2011.

UK VLF record - 2011

In 2011, I received G3XIZ (45km) which was the most distant UK amateur I copied sub-10kHz. I cannot recall the bandwidth, but it would have been very narrow.

Grimeton historic VLF CW transmission

Earlier this morning the historic alternator TX SAQ was sending a Christmas message on 17.2kHz CW. Years ago I got a QSL card from them. It is still on my shack wall. It is a good test of your VLF RX system. I did not listen.

VLF upconverter

There is a VLF upconverter on the DXexplorer website. On Christmas Eve there is a special transmission from the historic alternator 17.2kHz  CW transmitter SAQ in Sweden.

See https://en.wikipedia.org/wiki/Alexanderson_alternator .

See also https://alexander.n.se/en/

Please note, this converter is fine for a peek "down there", but amateur signals usually are weak and need very high stability, very accurate frequencies and very narrow bandwidths. Details of my own VLF experiments are on my main website.

VLF up-converter

Yesterday I had an email saying the link to this page on my website was not working. It turned out this link was to my old site anyway, so I have corrected the link to point to the newer site.

See https://sites.google.com/view/g3xbm4/home/vlf/vlf-converter .

A reminder that this extremely unlikely to work with amateur VLF signals which need very narrow bandwidths and very accurate frequency. It is, however, suitable for general listening "down there".

VLF earth-mode tests in 2011

 

As part of my experiments with VLF earth-mode was a test in 2011 at just over 17kHz using my 20m separated earth-electrode "antenna" in the ground.

VLF Sferics RX

 Listening to the natural emissions at VLF can be fascinating.  Not much is needed as this video shows. Of course, if the recorder does not provide DC power, you will need a source. In this case DC is provided by the recorder, so only 3 parts are needed.

I think this audio recorder is available on Amazon. On the DXexplorer site is another sferics receiver to drive headphones.

Receiving SAQ CW on 17.2 kHz VLF

This is a video about receiving the 100th anniversary transmission message in eastern Europe from SAQ in Sweden.

I did this some years ago and have a QSL card from them (see photo).

See https://sites.google.com/view/g3xbm4/home/vlf/vlf-converter .

VLF earth-mode beacon

 

Some years ago I really enjoyed experimenting with earth-mode VLF at 5W. I built a beacon TX and went out in the Fens trying to receive it. My best DX was about 6km, although I remain convinced much further would have been possible with more power and a bigger TX baseline.

Of course with hundreds of watts and a bigger earth-electrode baseline some radiation is likely, so hundreds of km becomes possible. With earth-mode most of the signal is conducted through the ground.

I had to stop when I had my stroke, which stopped me doing all sorts of field experiments. These days I hope others are carrying on where I stopped. Meanwhile I experiment, on something else, at home.

VLF earth-mode experiments

Back in 2013 I tried an experiment to see where my VLF earth-mode signal could be received in the car. 

My TX was 5W into my grounded electrodes. On RX, I dragged a resonant loop behind the car receiving on a PC.  The earth-mode signal popped up at odd points many kilometres away.. 

Since my September 2013 stroke I have been unable to do field work.

VLF earthmode

This was 14 years ago when I was still fit. I used to drive out in the car to see where my 5W beacon could be received.

ELF video - NOT amateur radio

For a long time, I have been fascinated by VLF/ELF radio communications. 

As you go lower in frequency, radio waves penetrate further through water and rock. For this reason, the military in many countries have explored these frequencies to communicate with deeply submerged submarines, although data rates at ELF are very slow and antennas very long. I know the Russians have a system at 80Hz (it has been copied in the UK), but I am not sure about the USA and China.

VLF memory 2011

 This was my copy of a VLF amateur signal from Germany 🇩🇪 on 8.97kHz with my earth-electrode antenna in the ground in 2011.

VLF transmitter

 

Looking through some old photos I came across this one of my VLF transmitter that was used for earth-mode tests though the ground. 

It produced about 5W and my best DX (before my stroke intervened!) was about 6km. Much further would have been possible.

Since my stroke, I have been unable to continue my VLF tests. It is still on my shelf.

VLF Earth Mode

Before my 2013 stroke, I enjoyed experimenting with VLF earth-mode, which anyone can enjoy. 

In the UK OFCOM is not interested in licencing this (and taking your money!), so anyone may make an earth-mode beacon. 

For the TX PA a low cost audio IC was used. It produced 4-5W.

Years ago I kept a blog of my exploits. I hope you can get some ideas here.

See https://sites.google.com/site/sub9khz/vlf-using-earth-mode/g3xbm-earth-mode-blog .

VLF RX loop

This was the RX VLF loop antenna I used for my earth-mode tests when I was fit. It was tuned to the RX frequency that was usually about 8-9kHz. The best orientation was with the loop  on the ground. The pre-amp in the blue box was tuned to the RX frequency.

As I recall, it was about 30 turns of 0.2mm PVC covered wire.

It is still in the back of the garage, I think. It is many years since I did any tests at VLF.

Amateur VLF

Amateur operation at VLF is very different from commercial VLF. In order to be detectable with "back garden" antennas and amateur powers, very high stability is needed and very long integration times. The latter may be hours or even days!  

Some years ago I was quite active on amateur VLF. On TX I experimented with 5W earth-mode and on radiated VLF I concentrated on RX and copied several Europeans below 10kHz. The photo shows G3XIZ (45km) although I regularly spotted German stations at far greater range.

Antennas were an 80m loop or my earth-electrode "antenna" in the ground at home and a portable multi-turned tuned loop or earth electrodes in the ground out portable. Out portable, the loop on the ground was the most successful.

Amateur VLF DX in 2011

 It’s some years since I did experiments at VLF. This was my first DX on 8.97kHz VLF.

VLF earth-mode experiments 2010

Way back in 2010 (when I was fitter!) I used to enjoy going out to see how far away I could detect my VLF earth-mode beacon running 5W. The furthermost I got was 6km, but much further would have been possible with more power and a larger baseline. Indeed, if the power is increased and the baseline larger I know of one station that has been received 100s of kilometers away. The RX station was able to detect the radiated component that was probably just microwatts. Earth-electrode "antennas" have been used successfully on  radiated tests at even lower frequencies with remarkable ranges being covered.