VLF amateur messages

From Eddie G3ZJO:

"Hi All
Since my last post Stefan DK7FC has been sending data using EbNaught on 8270.100 Hz. A 2 letter message was decoded by RN3AUS near Moscow a real first for Amateur operation.
Overnight on 17the Feb 2017 Stefan set the following challenge.

Let's risk something more again and try:

f = 8270.100000 Hz
Start time: Saturday 18.Feb.2017   18:00:00 UTC
Symbol period: 30 s
Characters: 7
CRC bits: 16
Coding 16K21A
Duration: 10h, 24m, 0s
Antenna current: 700 mA

By this time I was set up and operational for EbNaut after several Spectrum Lab freezes using the latest software release, and I had decoded theEbNaut files received by RN3AUS.
Next morning I loaded the overnight capture for decoding and concentrated intently on the computer screen.
Wow, in just 7 seconds ................... DREAMER
What a wonderful message for this iconic event on Sub9KHz, I didn't give thought to the significance of the test being 7 characters, expecting a dry radio call or expression. What could be better on the frequencies where we "are all dreamers and will never get any further than our own garden fence".
Today I can reveal the message as RN3AUS received it also and posted to the VLF Group. Currently there are 3 stations receiving EbNaut on VLF in addition the the 2 developers, Paul Nicholson and DF6NM plus DK7FC the TX'ing station.
DF6NM decided to run an EbNaut TX test concurrently with DK7FC on the night of 17th Feb. After the initial shock of decoding DK7FC I gave thought to looking for a 2 symbol decode, again in seconds appeared his message, a decode over a distance of more than 900Km. A surprise decode since I have not been able to spot his signal on my Spectrogram.
73 Eddie G3ZJO"

VLF kit at PA3CPM

Henny PA3CPM has been continuing his 8.270kHz VLF transmissions, on and off, for some weeks now and is getting reports from several stations in western Europe despite his modest antenna. Paul Nicholson in Todmorden and Eddie G3ZJO regularly receive his signals using integration over several hours and extremely narrow bandwidths to dig the signal out of the VLF noise.

8.270kHz VLF loading coil at PA3CPM

This is a photo of Henny's huge loading coil used to bring his 40m sloper to resonance on 8.270kHz. The loading coil uses a LOT of wire (several kms) and building such a VLF loading coil is not for the faint hearted! I suspect that a large wire loop may be an easier TX solution?

PA3CPM's VLF PA unit

Henny is using a 200W PA and this is shown here. Note the fans to cool the unit.

To radiate an amateur signal at VLF requires special dedication, yet Henny has shown that even a modest 40m antenna can get a signal hundreds of km on VLF with quite modest powers. It is indeed a new and exciting area of the hobby.

8.97kHz VLF amateur activity

DJ8WX's VLF signal received by G3ZJO (frequency is Hz)

This last week or so Uwe DJ8WX has been active again on VLF from his location near Hamburg.  Uwe was the strongest signal I ever copied on the so called "Dreamers Band" a few years ago and his signal is being well received again now. To copy these signals at 8.97kHz requires a quiet antenna location and a very stable, frequency locked receiver. You will NOT be able to hear anything and signals take hours or days to appear on the PC screen using a package like Spectrum Laboratory. Getting a very very stable receiver is actually easy as Spectrum Lab can lock onto one of the strong MSK VLF commercial signals and use this, or a GPS signal, as a very accurate reference. Much more details on the Sub-9kHz Amateur Radio pages.

First JT9-1 QSO on 472kHz

This afternoon I had my first digital 2-way QSO on the new 472kHz band using JT9-1 mode created by K1JT. The contact was with G3ZJO in IO92. Solid -15dB S/N reports were exchanged. I am still getting to grips with the JT mode procedure.

QRP JT9-1 QSO with G3ZJO today on the 472kHz band

 I also tried to work G3KEV on CW but he was unable to hear my QRP signal. I will try for more JT9-1 QSOs over the weekend.

2 countries worked on 500kHz with JT9-1 mode

Well, the JT9-1 test QSO with G3ZJO was a total success and completed in around 10 minutes this evening. Later, I called CQ on JT9-1 and got a reply from OR7T in Belgium who is 334km away. We worked, exchanging reports and 73s but I am not quite "all with it" with the sequencing of reports, R, RRR etc in JT mode exchanges.I am learning, HI.

G3ZJO in QSO with G3XBM this evening on 500kHz

The WSJT digital mode JT9-x is certainly an interesting mode. There are a few bugs in the code still, and more bugs in the operator using it (me!) but I am sure to use this mode more in future on 472kHz and 136kHz.

VLF DX radiated test results

My days long, continuous carrier test with G3WCD (32km) and G3ZJO (around 50km) around 8.977188kHz ended yesterday. I was using my 20m spaced earth electrodes with 5W out of the PA. The test was to see if anything at all could be detected well beyond the 6km I can repeatably obtain with QRSS3 earth-mode (through the ground) communications.  Despite the hint of a signal a couple of times on the G3WCD 45uHz and 22uHz grabbers, these proved to be false signals and nothing was detected.

Using Spectrum Lab, locked to a VLF MSK signal I am able to measure my TX frequency with VERY great accuracy, in fact to an accuracy of less than 1mHz. What this showed up was that my crystal controlled TX drifted (very slightly by HF VFO standards) about 13mHz over the 4 days of the test. Starting frequency was around 8.977177kHz and the final frequency 8.977190kHz. With shack temperature variations it may have moved slightly higher or lower too.

When the RX stations are looking for a very very weak signal in a bandwidth of 22uHz this means the signal is only "within band" for the FFT software to analyse for a brief period before drifting out of the measuring "bucket".  To have ANY chance it will be essential for me to lock the TX frequency so that it stays within a few uHz over a period of days. This could be done using a GPS reference signal or using Spectrum Lab. It is the latter that I shall be trying - receiving a VLF MSK signal on one antenna as the reference, then using SL to synthesise the continous TX carrier which is transmitted on a second antenna.

In reality to get 32km on VLF with my set-up was always a "long shot", but all parties agreed it was worth trying and we have all learned a lot in the process. Experimentation is the name of the game and failure is as important as success.

It may be some time before I try the long range VLF tests again: I hope to have over 100W next time and a super-stable TX signal. Who knows, we might just succeed next time.

For information on these software packages (all free) that I use at VLF see https://sites.google.com/site/sub9khz/software .

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.

G3XIZ a good signal on 8.976662kHz VLF today

Chris G3XIZ has just started TXing again and is a decent signal here in 424uHz bandwidth with the signal up to 20dB over the noise (see picture). Eddie G3ZJO was also getting a good signal. At 1530z Chris dropped the power 10dB but unfortunatley I was unable to copy at this QRP level, whereas G3ZJO was still able to.

DJ8WX on 8.970022kHz again

Just weak a very weak trace overnight (you have to look hard!) from DJ8WX on VLF. Compared with his signals a few days ago he is at least 10dB weaker. Not sure why as nothing has been changed here. G3ZJO also copied Uwe weaker than before, although Eddie was getting him slightly better than me using his E-field probe antenna. By the way, this small trace (in blue/white) covers a period of 8 hours and is looking for the signal in an incredibly narrow 424uHz (yes you read it correctly - microhertz) bandwidth.

G3ZJO in QRSS3 on 500kHz

G3ZJO has a QRSS3 beacon sending in FSK built in Altoids tins and running QRPp power. This is is a screenshot (from Spectran) of his signal this afternoon. I have superimposed his callsign, which is clearly visible on the upper line. The first dash of the G in his call is missing in my capture.

500kHz DX with 200uW ERP

Guess what?  Lubos OK2BVG has just spotted G3ZJO's tiny signal on 500kHz. Eddie is running only 200uW ERP. This evening conditions on 500kHz have been truly superb.

Another new reporter on 500kHz

Eddie, G3ZJO, has managed to copy my 500kHz WSPR beacon tonight. He is now the 13th station to hear me on the band. No great DX at 79kms, but pleased to be heard by someone else.

6m WSPRing and aeroplanes

Just been active on 6m WSPR this morning running 5W to the vertical colinear. The only person to report me, several times, so far has been G3ZJO who is 79kms to the west of me. What is most interesting are the number of multipath 6m signals seen on the WSPR waterfall with large amounts of Doppler shifts. G3ZJO has been analysing these are has made predictions about the aeroplane flight paths which would result in such traces. Here is the WSPR screen when receiving G3ZJO through an number of such multipath and Doppler shifted traces.

6m aircraft scatter

Just been WSPRing on 6m and spotted G3ZJO, who is 79kms from here, by aircraft scatter. This is clear from the WSPR waterfall display which shows all sorts of Doppler shifted traces as well as the one that was successfully decoded. I suspect this is aircraft stacked over, or approaching or leaving, Stansted or Luton Airports.

50MHz aircraft scatter

Interesting piece on G3ZJO's blog about 50MHz aircraft scatter using WSPR signals. He has a nice waterfall display showing the strange things that happen to a WSPR signal when aircraft are moving.