Sub 9kHz amateur radio

At one time I was very active monitoring amateur radio below 10 kHz. Stations from all over Europe were decoded. I also used to regularly run a website dedicated to amateur experiments at the very low frequencies. Some remarkable distances were spanned. 

To TX, very big antennas are needed. For RX an E-field probe, which is tiny, is very effective. Extremely accurate frequency control is essential. This is usually achieved by GPS locking or locking to a VLF MSK signal, which is what I did. Bandwidths are measured in uHz. Timescales are measured in hours or even days! Casual listening is extremely unlikely to result in success, except perhaps by earth-mode over much shorter ranges. 

Since my 2013 stroke, I have not been active below 10 kHz. Experiments continue and keen amateurs are still knocking on the boundaries and achieving what many thought was impossible.

The photo shows my reception of DK7FC in 2011. In more recent times he has been testing on ever lower frequencies and with earth-electrode antennas.

Sub-9kHz amateur radio

Some years ago I experimented on amateur radio below 9kHz. To receive amateur radiated signals at range needs very stable TX signals, very narrow filters and integration periods measured in hours or days. Just listening will not work! Luckily the software needed is freely available on the Internet. 

The photo shows G3XIZ. The frequency is Hertz!! My antenna was the earth-electrode "antenna" in the ground. 

It is some years since I last experimented on real VLF. As I recall, I copied amateur sub-9kHz signals from several European stations including 2 in Germany and 1 in Austria I think.

In the past I have successfully experimented at the far ends of the spectrum from visible light to far ELF. There is no doubt that we still have a lot to learn. At both these ends of the spectrum the equipment and test gear can easily be home-brewed. In many ways this is one of the attractions. My own VLF earth-mode gear was fabricated in the back of the garage as was my light beam gear: low cost and great fun. The second link includes a link to the files on my earth-mode article in RSGB RadCom in 2011.

See https://sites.google.com/site/sub9khz/

See https://sites.google.com/site/g3xbmqrp3/mflf

Some very old blog pages (which are not maintained so do not follow the links on the left) are at https://sites.google.com/site/g3xbmqrp/Home/earthmode. This is a blog about my own experiments with VLF earth-mode.

Sub-9kHz amateur radio

One of the websites I host is the Sub 9kHz Amateur Radio page. This tries to have recent news although many times it is better to look on the .io group in case I miss things. Most work is being done in Germany.

Sub-9kHz amateur radio on TV

How good is your German?

A recent ARD TV program had a bit on sub-9kHz amateur radio. Even though my German is almost non-existent it was good to put some real faces to people I had previously only known as callsigns. Even without any German language skills you can look at the pictures!

See https://www.ardmediathek.de/ard/player/Y3JpZDovL2JyLmRlL3ZpZGVvLzJlYWUzYWMxLWVhZDAtNDI2Ni05YjY2LWQ1NWQ1MDE3ODk5Ng/?fbclid=IwAR1SCzy2H_dqRGZwg1eEG60bDYAaIJvoKFI05cO0SgL1JGkD-uZlD2qJpA4

Sub 9kHz amateur radio

These days a dedicated bunch of amateurs continue to "push the envelope" by experimenting below 9kHz. At one time though getting outside the garden would be seen as amazing with the small antennas and low powers possible by amateurs. In actual fact amateurs have crossed the Atlantic! Although I don't claim to be always up to date, I try to be on my sub-9kHz website. If you are interested, take a look.

One myth is you need big antennas. On TX this helps with radiated signals, but on VLF RX they can be very small. An E-field probe just a few centimetres long can be very effective.

Sub 9kHz amateur radio

Although far from perfect, I try to keep up with the latest news about amateur radio below 9kHz. Quite a lot is happening.

Surprisingly, large antennas are not needed for receive and all the software you need is free.

This is one of the true frontiers in our hobby and access is easier and far less expensive than you might think. A perfectly fine RX setup can be made for a few cups of coffee in a café.

Most activity is just below 8.3kHz, which remains unallocated in many countries.

See https://sites.google.com/site/sub9khz/

Amateur radio below 9kHz

Until a few years ago, the conventional wisdom was that you needed huge power and huge antennas to be copied "beyond the garden fence" at VLF and ULF. In recent years much has changed and time and again great distances have been covered by amateurs with quite low power and modest antennas.

The trick is great stability, very narrow bandwidths and long integration times, often of days. For several years just detecting a carrier was enough, but in recent times people have been sending simple messages using EbNaut software.

When at the old QTH I detected signals from several European countries using simple, homemade gear and free software.

Although not totally up to date at all times, I try to update news of amateur VLF and ULF experiments at https://sites.google.com/site/sub9khz/ .

Amateur DX Europe to Alaska on VLF?

There has been some excitement over the last few days as Lawrence KL1X has seen a signal on 8.9700kHz when the noise was low that just could be coming from Uwe DJ8WX near Hamburg. He has tried to find out if this is a locally generated artifact, but it seems not.

KL1X grabber monitoring 8.270kHz for intercontinental amateur DX

In the coming weeks DJ8WX is moving his continuous carrier VLF transmitter (a long carrier is needed to be visible in the incredibly narrow bandwidths needed to see anything at all) down to 8.270kHz which is a clear frequency in Alaska. The Alaska VLF grabber is already active and, as soon as Uwe starts up, we hope to see a weak signal appear. If this happens this will be the very first confirmed reception of an amateur VLF signal from Europe in North America. The VLF receiver Lawrence uses is a small E-field probe antenna high up in a tree in a birch forest.

DJ8WX has been a very good signal on VLF here in the UK on my own receiving system (an 80m sq vertical loop feeding a preamp feeding a PC running Spectrum Lab with a special 424uHz bandwidth .usr file). I have not listened for Uwe recently as my loop is down but G3ZJO has copied him well in the last few weeks on his grabber.

DJ8WX's signal as seen on the G3ZJO VLF grabber

If you are interested in amateur VLF then visit https://sites.google.com/site/sub9khz/ and check out the various preamps, grabbers and DX reports. It is possible to check out activity by looking at the various grabbers (VLF receivers linked to the internet) around the world.

8.7 to 9.1kHz NoV received

This morning I received my NoV from OFCOM to operate legally around 9kHz (see copy on RHS - click to enlarge).

Details are:

• 1yr duration
  
• 8.7kHz - 9.1kHz 
• 100mW EIRP
• Modes not specified (long periodic modes preferred by Met Office)
• Met Office have to be informed of, and approve, operating periods and be sent logs
• Home QTH or /P locations only with prior Met Office approval

No firm plans yet when I'll start local tests on this band, but within couple of weeks with QRP WSPR and QRSS. I'll put a copy of the NoV on my website in the next few hours.

Sub-9kHz Amateur Radio group: 100+ members already

Since creating this new group on Saturday it already has over 100 members. Now we need to see some postings from people actually doing activity down there in the "Dreamer's Band".

See http://tech.groups.yahoo.com/group/sub9khz/

Sub-9kHz Amateur Radio (Yahoo group) formed

This new group is for anyone interested in amateur radio communications below 9kHz in the so-called "Dreamer's Band".  See http://tech.groups.yahoo.com/group/sub9khz/

VLF DX transmission with earth electrode transmission (49.6km)

DK7FC's 8.97kHz DFCW transmission received at 49.6km

Stefan DK7FC has informed me that he has successfully transmitted the message "CU" in DFCW on 8.97kHz to Michael Oexner at a distance of 49.6km. His TX puts out 250W into a 600m spaced earth electrode pair with a current into the antenna of about 0.5A. This is definitely far field reception. Stefan's earth electrode antenna is capable of further improvement, so he is expecting more successes shortly with it.

More sub-9kHz experiments

Just received this from Stefan DK7FC:

Dear LF/VLF,


Today i saw the first time a flag from Norway on my VLF Grabber (http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html). I would be very fascinated if my signal would be copied in LA/SM/OH  (of course, in all countries it would be very fascinating :-) ). Are there any stations, reading the reflector, from there who have the ability to receive on 8.97 kHz (or even 6.47 kHz) with a sensitive and stable RX frequency in DFCW-600 mode?
This would be one of my wishes for this period! One. ;-)
For this weekend i planned the next VLF experiment with the 200m vertical on 8.97 kHz but the wind forecast is not too promising :-( Maybe things look better tomorrow. I have to inform the air traffic control to give out a NOTAM (http://en.wikipedia.org/wiki/NOTAM), 48 hours befor i can start...
I will announce  tmw, if i will carry out the next test, if.
The signal would be once again the strongest i've ever radiated. About 50 mW ERP is the goal.
My planned tests for this year on VLF (kite antenna):
- CW QSO to DF8ZR (16 km distance) on 9 / 137 kHz
- Copying my signal on 8970/6470 Hz in Heidelberg in CW (40.0 km, audio recording and later analysis)
- Beeing visible in DFCW-120 in UK
- Beeing visible on the grabber of Renato Romero on 8970/6470 Hz
- Becoming QRV with the 300 m vertical antenna on 8970/5170 Hz, radiating 100 mW ERP at 8970 Hz
- Beeing visible in Russia and at all interested RX stations :-)
- Maybe a TA contact?
vy 73, Stefan/DK7FC *Dreaming...*

Sub 9kHz NoVs - a step nearer

The current UK applications for sub-9kHz NoVs have now been forwarded to the Met Office and I understand they have been received. With luck we may hear about the outcomes in the next few weeks. Currently there are 3 people appying for these G3XBM, G7NKS and G3XIZ. If these are successful I expect G3KEV and several others will also apply.

Diagram of my earth electrode antenna for 500kHz and sub-9kHz

This is a hand drawn diagram of my earth electrode antenna for 500kHz and sub-9kHz. On 500kHz WSPR this has managed to TX a signal as far as G0KTN who is 210kms away when using my 5W QRP transverter. Sub 9kHz my 4W TX is audible by ear at 0.5km range on an 80cm loop.  This is a totally "stealth" antenna that is not visible at all to anyone looking at the property.

4W TX for sub-9kHz experiments

Attached is a picture of the "transmitter" I'm using for my ground and induction communications tests. It uses a TDA2003 audio IC into a toroidal step-up transformer that can match from 10 to 150 ohms. Not sure of the transformer type which came from an old Pye Telecom PMR radio, possibly an M206, Whitehall or similar (it was used on the audio stages). I haven't yet tried listening with an active probe antenna to see how that would perform. Time is limited, so further tests may have to wait until the end of the month. Best range so far, receiving "by ear" on a loop antenna, with no clever selectivity or signal processing, is 0.35km.

VLF loop and up-converter ready for tests

This is a shot of my receiving loop antenna for sub-9kHz local earth-mode and induction comms testing. The loop consists of 30 turns of wire on a wooden frame. This feeds into my SBL1 based VLF-to-HF up-converter (the small blue box on the frame). The output of the converter feeds into the FT817 receiver.

Sub-9kHz NoV - still awaiting Met Office OK

I chased Rod at OFCOM this weekend to see if there was any further news on the NoV application to TX below 9kHz. The hold-up is still the Met Office, from whom OFCOM are awaiting approval. I'm carrying on with sub-9kHz earth-mode and induction tests at 4W meanwhile as I can't imagine anyone will object. My transmissions last about 10 minutes and the radiated power is picowatts!

Talk request from Peterborough CLub

Having given a talk about "kitchen sink" simple radio last year, the good folks at Peterborough have kindly invited me back to talk about sub-9kHz radio. Date confirmed as Wednesday Aug 25th 2010.

Sub-9kHz NoV application being processed

Rod Wilkinson confirmed that he's received my application today at OFCOM:

Hi Roger,

Many thanks for your email and you will be pleased to know that your application has arrived on my desk this morning, I am sure all will be in order.

As mentioned earlier my colleagues have contacted the Met Office but we are awaiting their response, I am afraid this may not be a prompt process.

I will keep you updated as we progress but if you do wish to check on the status please do contact me.

Vy 73

Rod