8.76kHz field testing in the snow at 1.5km

With a temperature around 0 deg C I did a field trip today TXing on 8.76kHz VLF to test two things: (1) to check the rebuilt 4-5W TX based on the TDA2003 could be copied at moderate range and (b) to try out the new tuned preamp with earth electrode receive antennas and see how these compared with a loop. The usual first test site, a National Trust car park about 1.5km from home was chosen. Today it was totally deserted with more sensible people curled up in front of warm fires. Using the 80cm receiving loop or with the earth electrode antenna (electrodes placed about 13m apart) decent

copy was achieved in QRSS3, using Spectrum Lab this time rather than Spectran on the PC.  For the earth electrodes I just used barbecue skewers pushed in about 10cm into the very cold ground. Reception was also possible with the two earth electrodes just 2m apart. The first picture shows the signal received with a loop. The second is with the earth electrode antenna on receive. The ground was covered in a thin layer of wet snow and results when the soil, and soil surface, are dry should be better on earth mode conduction using earth electrodes at each end. The roads in the Fens were too icy to try reception at a more distant point 5-6km away. Also, I need a much longer baseline earth electrode pair in the car in case this is needed at greater range.

New front-end for 8.76kHz VLF earth mode tests

Today I completed the design of a new "front-end" for my tests on 8.76kHz when using earth electrodes as the RX antenna. Up to now I've used an 80cm loop/preamp at the far end of the test, usually with the loop on the ground for maximum signal pick-up. Now I want to compare results with an electrode pair antenna at the RX, laid across the road to form a pickup loop within the ground around any buried pipework and cables. The electrode pair is about 30-100 ohms, so I needed a low input impedance. I decided on a grounded gate FET amplifier with a simple LC tank circuit in the drain tuned to 8.76kHz fed via an emitter follower into the PC sound card. It has sufficient selectivity to reject 50Hz and lower harmonics and reject the stronger VLF and LF stations which could cause intermod and overload. I've also added a small LC lowpass filter on the input to the FET. This will be field tested at a site 5.3kms from the home QTH as soon as the weather improves: it is currently below freezing day and night!

Receiver/grabber improvements on VLF

Just received a special build of Spectran from Alberto I2PHD that keeps the same filename for captured grabber images. This means I can now use Spectran with my VLF grabber. This is fired up from time to time when people are doing VLF tests. It will also allow me to look for my own signal at home when I am out transmitting in the Fens locally some kms from home. I find Spectran easier to use than Spectrum Lab, which is a clever program but complicated for someone like me to configure.

I have also rebuilt the 4-5W beacon TX on 8.76kHz and given it a 1 hour continuous soak test. There is a video about this on my YouTube channel.

My next job is to work on a permanent VLF E-field probe outdoors and to make improvements to the receiving system for field use. I need a better preamp/filter that can also be used with earth electrode receiving antennas as well as the loop and E-field whips.

Looking for G3XIZ on VLF this evening

G3XIZ is transmitting with 20W to his Marconi vertical on 8.9719kHz this evening from 2000-2200z. I am looking out for his signal with my loop into both Spectrum Lab and Spectran software. You can look on my VLF grabber to see if he is visible at all over here in JO02dg. At the moment all that is visible is a wobbly 50Hz related signal and my 8.760kHz QRSS3 beacon running on a dummy load. UPDATE: nothing copied and Chris had to close because of an antenna fault at 2100z.

VLF Grabber operational capturing 8-9kHz in JO02dg

I'm setting up a VLF grabber at my home QTH to take periodic screenshots of the 8-9kHz Dreamers Band and make these available online. At the moment it is taking input from my earth electrode "antenna" into Spectrum Lab and is very much a work in progress and needs a lot of improvements on the RX and antenna front. It won't be ON unless I'm in the shack and don't need the PC for other VLF stuff.  

The resulting screen grab every few minutes appears at https://dl.dropbox.com/u/15047843/xbm_grab.jpg . 

VLF Grabber

Today I intend to make a VLF grabber to receive sub9kHz signals and automatically upload the screen grabs to the Internet. My aim is to use Dropbox as the place where the grabs will we stored and visible.

6 Spanish stations get access to 501-504kHz

The Spanish authorities have granted limited access to 501-504kHz (100Hz bandwidth, 5W) to 6 stations (EA1AY,  EA2HB,  EA3CC,  EA3WX,   EA4BVZ, and  EA5DY) until the end of May 2011,

iPod Touch 4g

Recently I upgraded my pocket PC - I used a Dell Axim for 7 years - to a new iPod Touch 4g purchased at a good price from Amazon. It really is an amazing piece of kit in a tiny size with an incredibly pin-sharp screen which is so good that individual pixels cannot be seen: the resolution is better than my TV. I've already downloaded the Echolink app (free) so I now also have a 2.3GHz pocket ham transceiver too. I hope to use it for some other ham radio applications including datamodes and VLF reception.

If you want to see what is inside the iPod Touch 4g look here for a tear-down analysis: there is a lot in this small package!

First Norwegian VLF amateur transmission

From Jan LA3EQ:

"First succesfull transmission on 8.760kHz using WSPR mode in Norway using 40 meter longwire and only speaker output from the pc soundboard as a transmitter and a 12volt to 220v transformer as impeadence "antenna matching" transformer..  Several WSPR spots of -2dB to -7 dB. distaince only 50 meters, but it is a start. Next try will be with earth dipole and 10 watts and an active e-probe antenna on receive."

VLF kite transmission by DF6NM

DF6NM's signal in the UK

Marcus DF6NM carried out another successful VLF test yesterday on 8.97kHz (200uW ERP) and 6.47kHz (50uW ERP) with reception by Paul Nicolson in Todmorden UK.  Marcus is the second German VLF amateur to be copied at this distance.

Inactive week radiowise

This week I've been very inactive on the radio because we have had our grandson's 3rd birthday party here with his French grandparents (neither of whom speak English) staying along with his mum and dad. Still, a lovely time was had and he got lots of nice presents. By the way, he now knows the difference between square waves and sine waves and loves going "oo oo", which means fiddling with the audio oscillator and scope.

Looking for G3XIZ on 8.9719kHz VLF

Looking for G3XIZ on 8.9719kHz - maybe a faint trace??

Between 2000 and 2200z this evening G3XIZ has been transmitting on 8.9719kHz VLF with his Marconi vertical and about 20W RF into it. I've been monitoring with my earth electrode antenna, a preamp/filter and a PC running Spectran on 0.17Hz resolution, but don't think I've seen any sign of him.

Real QRP on 8.760kHz today

Weak trace at 1.5km from the 320mW TX by earth mode

320mW 8.760kHz QRSS3 transmitter

Having blown up my 4W transmitter yesterday I built a smaller QRSS3 beacon TX today that puts out 320mW into 50 ohms. I connected this to the earth electrode antenna and went out with the loop and E-field probe and PC to see how it performed. The signal was copied weakly but solidly at 1.5km away at the local National Trust carpark (see picture from Spectran showing the XBM part of may callsign). An attempt at 5.1km was unsuccessful although faint traces of the line at 8.760kHz may have been visible.

How to be stupid ...follow me

Just managed to blow up my 8.76kHz TX by putting the supply the wrong way round: took out the 4060, 5-Vreg and several electrolytics.The TDA2002 was also damaged. Rebuilt the keyer and freq gen part OK but now need to source a new audio PA IC or module. Now I have a reverse protection diode across the pins! You learn the hard way.

In the meantime I may try even lower power with my trusty 2N3904/3906 1W PA and see if this can be seen at the NT carpark (1.5km) and at Lord's Ground Farm (5.1km). Also, as this PA is efficient and runs cold for ever I could try 1 day on, 1 day off, QRSSSSS and see if more distant people could copy it using very narrow bandwidth reception as per DK7FC's tests.

QRP at AA1TJ

It's time to remind people of the wonderful circuits and ideas at Mike Rainey AA1TJ's site. Always full of amazingly simple designs that really work. See  http://www.aa1tj.com/radio.html

UK first transmission on the Dreamer's Band (8.760kHz)

Signal received at 5.1km from home QTH on 8.760kHz VLF

This morning 0915-1115 GMT I transmitted a QRSS3 beacon signal on 8.760kHz under the terms of my NoV recently received.  I think this is a first in the UK, legally at least.

8.76kHz TX

TX was 4W from a TDA2002 audio IC matched into earth electrodes 20m apart. The beacon signal was provided by a K1EL keyer chip and the frequency reference by dividing down an HF crystal by 512 times in a 4060 divider IC. Reception was possible 5.1km away from the transmitter location, detecting the signal with an 80cm loop fed into an E-field probe (Hi-Z input) into Spectran running on a WinXP PC. Best reception was always with the loop flat on the ground suggesting the main mode of propagation is utilities assisted earth mode. Comparing results on 8.76kHz with those at 838Hz earlier in the summer, my first impressions are that signal levels are some 6dB weaker, but more careful tests will be needed.

500kHz interference

In the last few days several stations across Western Europe have noticed a strong wideband signal that is severely impacting reception between 498-502kHz. This appears to be a NATO test transmission for a marine data system that may be introduced in the near future.

8.75kHz VLF transmitter ready

My small 4W, crystal stabilised, 8.750kHz VLF transmitter is now ready to test having fitted the crystal and 4060 divider this morning. All being well I'll test this Wednesday or Thursday when I've optimised my soundcard settings on the PC used at the RX end.

Preparations for Dreamer's Band Tests

This evening I modified my loop antenna and VLF preamp to better optimise them for use at 8-9kHz and also modified my E-field probe antenna. So, on the RX side I think I'm ready with the hardware. By Wednesday I hope to have the 4060 divider behind the HF crystal to give me a stable 8.750kHz source for the TX. If the weather is reasonable I should be out testing in the Fens locally by Wednesday or Thursday.

First "Dreamers Band" UK test next week

As is required by my NoV, I asked the Met Office for permission to transmit in the 8.7 - 9.1kHz band next week Tuesday to Friday 0800-1800 GMT and they've confirmed it's OK.

My initial tests will be a repeat of the earth-mode tests done at 838Hz earlier in the summer using the same kit  with 4W to 20m spaced earth electrodes. I'll also test with the 70m sq wire loop antenna used for 136 and 500kHz. The most likely TX frequency will be 8.750kHz (4.480MHz xtal divided by 512). I'll find a means of getting on 8.970kHz later. Modes will be 12wpm CW and QRSS3 initially.

These local tests are not in the same league at all as DK7FC's and I'm only expecting a few kilometres at best. However, it is a start and it allows me to test TX and RX equipment and different PC packages.

6 countries on 500kHz tonight

Another good night on 500kHz WSPR with several more reports from Finland (OH1LSQ) as well as a report from Norway (LA3EQ) and several from nearer countries. ERP still in the 1-2mW region from the loop antenna.

Protecting power grids from solar storms

NASA Science News reports:

"Every hundred years or so, a solar storm comes along so potent it fills the skies of Earth with blood-red auroras, makes compass needles point in the wrong direction, and sends electric currents coursing through the planet's topsoil. The most famous such storm, the Carrington Event of 1859, actually shocked telegraph operators and set some of their offices on fire. A 2008 report by the National Academy of Sciences warns that if such a storm occurred today, we could experience widespread power blackouts with permanent damage to many key transformers."

There are plans afoot to create an early warning system to protect the US grid system in such events.

More DX reports on 500kHz

Log from early evening Oct 26th 2010 (500kHz QRPp WSPR)

This evening, the QRP 500kHz signal from the small vertical wire loop is doing well with reports again from Finland on WSPR. I still can't quite believe how a loop of thin wire with part of it sitting in the wet grass can work so well with so little power applied to it.

Stable, simple, stand-alone, 8.970kHz source?

What do people think is the simplest way of generating a stable 8.970kHz (kilohertz) frequency that does not require a PC when running? I thought of an HF crystal divided down by 256, but have you tried to buy a "made to order" crystal lately? I need this for my VLF tests this coming winter.

Vertical loop versus earth electrodes antenna

Just done an interesting test comparing my vertical wire loop with an earth electrode antenna. I removed the lower part of the loop and connected the ends to ground. Matching was totally different (low Q antenna) but the performance was only 5dB down on the loop, based on reports from 2 local and one DX station. A similar test on 136kHz as the only station on in range (M0BMU 69km) was unable to copy my signal on the earth electrode antenna suggesting at least 5dB down on that band too.

Amateur VLF update: reception in 8 countries + 1310km DX!

DK7FC's summary of reports on Oct 23rd 2010

DK7FC has now summarised last weekend's test results on VLF (see table attached). His mW ERP signals from his kite antenna were received on 3 different VLF bands at distances up to an incredible 1310kms!
Stefan has certainly shown how to do it.

136kHz ERP

A fairly easy way to increase my ERP on 137.5kHz WSPR is to up the supply voltage to the IRF510 PA. Using a 20-24V supply I was able to get another 3-4dB ERP judging by the reports from M0BMU and G3WCD this morning. This evening I'll give it a go with the higher supply to see if I can get any reports from further afield. I've also thickened up the bottom part of the loop which will reduce the resistive losses by about 15%.

DK7FC's VLF tests a great success

Stefan's latest VLF kite antenna transmissions at 8.97kHz and even lower frequencies were a great success yesterday with reception as far as Eire, Italy, Poland and the UK. The attached shot shows the signal on 2 frequencies as received by Renato IK1QFK in Italy.

M0BMU receiving DK7FC's 8.97kHz signal 10dB S/N

Jim reports that Stefan's DK7FC's 8.97kHz test signal is visible at 10dB S/N in Tring UK this morning. He is also visible on other grabbers in Europe. This is an excellent report and further encouragement for those of us taking our first (QRP) steps on the 33km band.

More 500kHz 2mW ERP DX reports this evening

This evening I switched back to 500kHz from 137kHz WSPR earlier in the day. Yet again good WSPR reports from GM4SLV and OH1LSQ (1733km) who received me as early as 1716z.

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.

Struggling on 137.5kHz

Using the same TX output power (5W) and the same loop antenna I'm finding life is VERY much harder on 137.5kHz compared with 500kHz. Last night I was being copied right across Europe on 500kHz but tonight only 2 stations (best DX 69km) are able to copy me on 137.5kHz WSPR. The reason is simple: the radiation resistance is so much lower, so losses become more significant, and the ERP is very considerably lower. There is no doubt that to increase my "sphere of influence" on 137.5kHz I'll have to make some big improvements.

New DX record on 500kHz WSPR

This evening, quite unexpectedly, I got a string of reports on 500kHz from OH1LSQ in KP03sd at an astounding distance of 1733km. To me these are amazing reports pushing my best DX on the band with just a few milliwatts ERP to new levels.  What surprises me is how well a very simple wire loop works as a TX antenna: the wire is just 1mm diameter, with a loop area of around 70m square with part of the loop on the ground buried in wet grass. I now believe almost anything is possible!

Vertical loop success on 500kHz QRP

This evening I've been WSPRing on 500kHz running about 2mW ERP from my thin vertical wire loop with an area of around 70 sq metres. The bottom of the loop just runs along the ground and at the moment is buried in the long wet grass! Despite this, my signal is being decoded in G, ON, PA and GM with best DX tonight 896km to GM4SLV up in the Shetland Is.

Further 8.97kHz test this Saturday

DL7FC, Stefan, is planning another VLF kite antenna test this weekend Oct 23rd. I am assuming he will be on 8.97kHz again.

Additional SAQ VLF transmission

From SM6NM/Lars

There will be a transmission with the Alexanderson alternator on 17,2 kHz on United Nations Day Oct 24 2010 at 11:00 UTC. Start up and tuning from about 10:30 UTC. This time we do not require any QSL-reports and will not verify. We intend to continue with our annual transmission on Christmas Eve (morning), Dec 24, at 08:00 UTC with tuning up from 07:30 UTC. D.S.

 

Holiday in South Africa - just back

No posts here for the last few weeks as my wife and I had been on holiday in South Africa. It was an amazing holiday organised by Saga and we saw some fantastic places, people and animals. Saga organise holidays for the over-50s and we were not sure what to expect, but the hotels, food, transport, and everything well exceeded expectations and the group we were with was a real mix of interesting people. The whole experience was something to feed on for years to come. For example, seeing the "Big 5" wild animals (and many more) in the Kruger National Park, seeing no less than 6 southern right whales at one spot from the shore near Cape Town and getting to within a couple of metres of wild penguins on a beach near Simonstown. Also, seeing the highlands of Lesotho where people still live a subsistence existence in huts made of dung, straw and sand without electricity and the basics we take for granted.

8.97kHz DX tests Oct 2nd 2010 (DK7FC)

Stefan's latest tests are going well with copy at 902km (Poland) and in Holland and the UK. His signal is stronger than ever before. Well done Stefan. Some stations right across Europe and even in North America are watching.

10m WSPR DX

For a change I went onto 10m WSPR today and was rewarded with a -26dB S/N report from FR1GZ on Reunion Island (9724km away) when I was running 5W to the halo.  Interesting to note the Doppler shift on the signal (and also on the signals from FR1GZ) which suggest movement of the equatorial F layer.

Earlier in the afternoon ZD7FT was a reasonable signal on 10m SSB from St Helena and there were several VE and W's on 15m SSB.

More German VLF radiated DX tests Sat October 2nd

From Stefan DK7FC:

Dear LF/VLF,

My next VLF kite experiment will be tomorrow, saturday, 2nd october :-) After my request to the german air traffic control i got a very kind telephone call at 01:30 AM and later i got the permission to go up to 200 m above ground. See attached mail if of interest for you.

So, if there will be enough wind and no rain, i will try to become QRV at arround  8 UTC.

Tomorrows program:

- (after some resonating tests): Transmitting a short message on 8970 Hz, mode: DFCW-600, hoping to be visible on several receivers in the EU region and maybe Canada and USA (!?)
- Transmitting a CW message (in 12 wpm and in 25 wpm), hoping to be audible at Bernd/DF8ZR (16 km range) and my grabber (40 km)
- Maybe trying a xband QSO 9kHz/144 MHz to DF8ZR
- Transmitting a message on 6470 Hz, mode: DFCW-600, hoping to be visible at many RX, especially Renato Romero who has set up a grabber page at http://www.vlf.it/cumiana/livedata.html
- Transmitting a 30 minute carrier on 8970 Hz which allows long time integration. Paul Nicholson wants to try to record the VLF audio stream from Florida and maybe extract my signal.

- Being visible at PA3FWM at the university of Twente who set up a grabber page at http://websdr.ewi.utwente.nl:8901/grabber.html
- Being visible at SQ5BPF and maybe a russian station?
- Being visible at Paul Nicholson and Markus/DF6NM, of course ;-)
- Finally reaching the 1 A antenna current limit
- and all i have forgotten

I will record my signal of my grabber and will extract an audible signal, if possible. This will be filtered, frequency shifted to 800 Hz and published here as a mp3 file.

My grabber will show the 8970 Hz signal at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html
The 6470 Hz will be visible at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html

It is now on the Canadian and US RX stations to make possible what still seems to be inpossible: A transatlantic transmission/reception. The first time my signal can reach a 50 mW ERP limit (wind forecast announces strong wind, so a high kite angle, so a good efficiency!) on 8970 Hz. It is still not sure how the propagation behaves on this frequency at this time and locations so we may see a surprise. Of course any report is very much appreciated, no matter of what distance or country. Every clear reception above 859 km is a new world record by amateurs on VLF!

So, hope the sun will shine at good wind conds and low QRN and high interest :-)

Best 73, CU, Stefan/DK7FC

PS: Markus/DF6NM, will you be on the phone again to make QSP? :-)