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.

VLF upconverter

Many people want to take a peek at what is on VLF. The problem is that many receivers do not tune that low. One answer is an upconverter so that VLF is translated to a frequency covered by a conventional receiver. 

For amateur VLF signals, this is extremely unlikely to be useful as VLF amateur signals need great frequency accuracy, extremely narrow bandwidths and long integration periods measured in hours or days. 

For VLF utility stations this upconverter will be useful.

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

2011 VLF memories

 Before my stroke I really enjoyed experimenting with both ends of the spectrum. I quite enjoyed seeing how far I could get on VLF earth-mode through the ground. This was a Facebook memory from 2011.

VLF earth-mode TX

Looking back over some of my old photos, I came across this photo of my 5W earth-mode VLF transmitter, that was last used over 10 years ago. 

The 3C90 toroid on the left is to match the low impedance output from the TDA2003 to the earth-electrode "antenna" in the ground. In the centre is the TDA2003 audio amplifier. On the right is the keyer IC that can produce QRSS or CW.

It would be good to do some more experiments in the future, if my health allows.

Amateur radio below 9kHz

 

This was 2011. It is a long time since I did experiments at sub-9kHz

Sub 9 kHz DX

Some years ago, I was quite keen on amateur radio below 9 kHz. I well remember people saying it was a waste of time and nobody would get beyond the garden fence. How wrong they were!! Some quite remarkable distances have been spanned. 

Although for radiated DX below 9 kHz very big antennas are needed for TX, on RX some tiny antennas can work perfectly well such as an E field probe which is tiny. What is needed is very high stability and very narrow bandwidths, usually achieved by locking to a VLF MSK signal or GPS. Some years ago DJ8WX was spotted by locking to a VLF MSK signal (see photo). All this was possible with free software. Sometimes it is necessary for signals to be integrated for hours or even days.

It is some years since I have experimented at real VLF.