VLF Amateur News 2017

Dec 28th 2017

It appears we have a new VLF world record!

Thanks Paul and Renato! What's next? WX for today looks questionable but the next few days may be ok.

Dex

On Wed, Dec 27, 2017 at 2:21 AM, Paul Nicholson <vlf0403@abelian.org> wrote:

W4DEX wrote:

> 3 chars 16K21A CRC20

> 30 second symbols

> Start 22:30 UT

Success!

Decoded 'QRZ' at Cumiana (IK1QFK) with

Eb/N0 = +0.4 dB, BER 41.6%;

S/N -31.7 dB in 1Hz, -65.7 dB in 2.5kHz

(after sferic blanking);

List rank 5689, constant reference phase;

Distance is 7173.4 km which is a new world record for

VLF message decode and a record distance for EbNaut

at all bands.

Predicted Eb/N0 was +0.6 dB.

Decoded via the live VLF stream from Renato's E-field

receiver.

These two stations already hold the record distance for

carrier detection at VLF. This result extends that to

a message decode.

Signal data available in vlfrx-tools format:

http://78.46.38.217/w4dex-171226-vlf15.vt

Decode with

vtraw -oa w4dex-171226-vlf15.vt |

ebnaut -dp16K21A -r1 -S30 -k20 -N3 -v -PU -L500000

Congratulations to both stations for a great result.

--

Paul Nicholson

Dec 14th 2017

A reminder from Paul Nicholson to the RSGB's LF reflector about getting active at VLF:

Perhaps the perception is that it is difficult? Surely not.

Don't believe all those stories you hear about how hard it is

to radiate, or how difficult it is to find a location to

receive from!

Let's see -

- Low cost. You don't need expensive SDRs or test equipment.

Your PC soundcard is signal generator, spectrum analyser,

and SDR, all in one. Transmitter is just an audio amplifier,

even a low quality one. The most expensive thing you'll buy

is a load of wire for a loading coil.

- GPS timing? £18 quid for a NEO-7 module and you know your

frequency to the micro Hertz. Buy two, you'll use them!

- Easy to build. Just audio frequency signals, nothing critical

about layout. VLF is great for the homebrew enthusiast.

- You don't need a huge ERP. 10uW and you're on the air. Your

LF antenna will probably do better than you think at VLF.

- UK Notice of Variation? No problem, a simple application form,

and if enough apply, maybe the regulators will make that easier.

- Where else can you operate at the cutting edge with such

simple equipment?

In case you thing my location here is specially good, it certainly

isn't. The mains here at the top of the Calder Valley is very

rough, terrible sidebands. All the properties around here get

their power by overhead lines at 12kV and one of the two 33kV

lines feeding Todmorden is only a km away. The nearest 12kV

line is just 120m from the E-field antenna. 140mV RMS of 50Hz

on the E-field probe and a lot of harmonics. Reception here is

bad! You can probably do better in the suburbs.

How many times per century does amateur radio find a green field

to explore? Not just a new band but a whole new frequency range.

Don't miss out on this one!

--

Paul Nicholson

December 12th 2017

Fantastic! My congrats to IW4DXW, the first VLF amateur radio station (at least in this century :-) )!

Am 12.12.2017 09:12, schrieb Paul Nicholson:

http://abelian.org/vlf/tmp/171212a.gif

VERY nice!

So theoretically there can be 6 TX stations on the band meanwhile!

IW4DXW

DF6NM

W4DEX

DK7FC

DJ8WX

VO1NA

We should try to transmit during the same time some day to produce 6 peaks on Pauls RX site :-)

Good luck and progress Riccardo. Your station looks very good. I have 480 pF here, about the same capacity. So we could exchange our coils ;-)

73, Stefan

December 3rd 2017

Dreamer's Band Success "across the pond"

Two T/A signals at the same time, and on almost the same

bearing:

VO1NA 280.1 deg at 3575.4 km

W4DEX 284.6 deg at 6194.2 km

This couldn't have happened any better if we'd planned it.

Perfect timing by Dex to come on to 8270 when he did.

Markus wrote:

> The directional lobe seems rather sharp

The bearing of each Fourier bin is calculated (mod 360) and

any bins which have bearing outside a +/- 20 degree band around

the chosen azimuth, are suppressed by setting their magnitude

to a small value. This is the 'filtered bearings' part of it.

That gives the impression of sharpness as you swing the compass.

The bins which survive the filtering then have their magnitudes

re-calculated by synthesizing a cardioid aimed on the bin's

bearing. Thus we obtain some extra gain in the forward direction

and a null in the opposite direction.

It is possible to run without the bearing filter stage, then you

just get the cardioid response. This may be better in some

situations. I've got a slicker version of the spectrogram

in the pipeline and that will have the option to filter bearings

or not. But I won't try to finish that until I've upgraded

the H receiver.

> What is the latency between the end of a one-hour buffer and

> the time the latest spectrogram comes online?

About an hour.

> are you still using three separate stereo soundcards with

> individual timing corrections,

Still three M-Audio 192 PCI cards 24 bit 192k/sec. Each has

VLF signal into one channel and a shaped PPS into the other.

Three instances of vtcard and vttime, and a vtjoin to align

them by timestamp. The result is a 3-channel stream.

Various things T-off that. A vtresample to 48k/sec and

a vtwrite records /raw continuously and the spectrogram

dips into /raw with vtread to grab one hour segments.

> Could downconvert-and-decimate be used to speed up FFT

> calculations for the narrow spectrogram?

The one hour segments of 3-axis stream are passed through a

vtfilter which applies the phase EQ for each channel, then

through the sferic blanker, then mixed down and resampled

to 240 samples/sec before the bank of Goertzel filters.

I don't think it would be any quicker to replace the Goertzel

bank with a fast Fourier transform.

I'm very keen to eliminate the three PCI sound cards and replace

them with one capture device but so far I haven't found one

good enough.

Paul Nicholson

November 14th 2017

More 8.27kHz tests from DK7FC:

VLF,

Tonite, a new attempt to leave a 3 char message at RC4HAA and an invitation to newcomers:

f = 8270.1000 Hz

Start time: 14.November.2017 16:00:00 UTC (daily)

Symbol period: 60 s

Characters: 3

CRC bits: 10

Coding 16K21A

Duration: 12:48 [hh:mm]

Antenna current: 650 mA

73, Stefan

PS: The sun is back, the grabber is back! :-)

November 13th 2017

Stefan DK7FC is planning tests on even lower frequencies:

Today i searched for suitable materials to build a iron band rod for a coil for 970 Hz.

I learned about kornorientiertes Elektroblech, https://de.wikipedia.org/wiki/Elektroblech or https://en.wikipedia.org/wiki/Electrical_steel

A normal 50 Hz transformer is using 0.5 mm plates. For higher frequencies there are thinner plates available.

I searched for a local company and quickly found this product catalogue:

http://www.lohse-ringbandkerne.de/uploads/downloads/Lohse%20Prospekt%20D_web_2017.pdf

Excellent! They offer 0.23 mm think plates.

Then i sent them an email request and later i had a telephone talk with the chief of the company. I asked if they have maybe even better materials and he said yes, they have a band of the type H075/18/20. This is a band which has a thickness of just 0.18 mm and it is 20 mm width. Since it is grain-oriented it matters how the B field passes through it.

He said that this special band is worse at 50 Hz but can be used to up to 4 kHz!!!!!!!!!!!!!!!!!!!!!!!!!!! So maybe this opens the frequency range from 4 kHz down to the lower ULF!!!! :-)

I got a good price, just 4 EUR for 1 kg but i have to order at least for 100 EUR so i will order 25 kg of that stuff! Already done!

My idea is to build a 0.5 m long rod. One piece of the band will then have a cross section area of 3.6 mm^2. I will need about 1000 to 1500 of these bands in parallel. This should fit into a PVC tube with an outher diameter of 80 mm. Very handy!

I'll keep you informed ;-)

73, Stefan

November 12th 2017

DX on VLF continues. See this message for DK7FC:

Hello VLF group and RC4HAA team,

I am glad to report about the successful decode of my 1 character EbNaut message on the VLF RX site at RC4HAA.

This is a land path distance of 2877 km, http://k7fry.com/grid/?qth=JN49IK00&from=LO53CF34

So far the best DX between Germany and Russia below 9 kHz.

It is my new personal ODX on VLF (the old ODX was just 4 km shorter).

A screenshot of the decoder result as well as the log file is attached. The unexpected good SNR suggests that even longer messages are possible within a single night. Also we need to consider that it was a very noisy night again, with thunderstorms in Spain and Italy.

A new message announcement will follow soon, next time i'm trying 2 characters.

October 27th 2017

VLF transmissions from DK7FC continue. The Paul he mentions is in the UK (Todmorden).

"Hi Paul,

Since 13:20 UTC im running 120 mA on 3 individual frequencies:

5090.005 Hz | 5130.005 Hz | 5170.005 Hz

The phase and current of each carrier is individually hold constant.

It is a sponatneous ideo to do that. Hopefully your RX is available in the moment. I will announce the end of the transmission later. Maybe with 3 hours you can find 3 peaks beeing significantly stronger than the noise background. It would be interesting to see if there are significant differences in the signal strength on our path...

73, Stefan"

October 7th 2017

Transatlantic (Canada to UK) 8.27kHz

VO1NA on 8270.00709 is a good nighttime signal at Todmorden

recently. Here are the last three night's spectra in 34.72 uHz

(8 hours 23:00 to 07:00 UT) using combined E-field and H-field.

http://abelian.org/vlf/tmp/171007b.gif S/N 12.6 dB

http://abelian.org/vlf/tmp/171007c.gif S/N 14.5 dB

http://abelian.org/vlf/tmp/171007d.gif S/N 11.4 dB

Not bad for 8uW ERP at range 3575 km and an undisciplined

OCXO.

Paul Nicholson

October 6th 2017

EbNaut tests are continuing at various VLF/ULF frequencies. Marcus DF6NM is having success decoding Stefan's transmissions.

Despite truncated data from a 31 uHz instance and severe railroad QRM, I happened to get a correct constant-phase decode from my home antenna.

Best 73,

Markus

September 17th 2017

All right. After the currently running experiment i'll run some carrier or maybe DFCW-60000. I'll announce it a few days before.

Make sure a 47 uHz window is running to that time, maybe two Spectrograms, one showing 8270 Hz, the other one showing ALPHA F1, 11904.7619 Hz.

Locking to GBZ or GQD or 1 PPS is a requirement! Maybe Eddie can help you if necessary.

73, Stefan

Aug 24th 2017

Activity from North America on 8.270

Testing the coil amp and dds in anticipation of experimentation

this fall and winter. 8 uW.

Unfortunately it is undisciplined so QRG is +- a few ppb until the

NE0-7M gps module arrives.

73

Joe VO1NA

Aug 20th 2017

VLF earth-mode in the UK from Jim G7NKS. He is using 300W

Hi All

I’m running a VLF test beacon on 8.9kc . Ground loop electrode system. 35m long

Any spots welcome (if unlikely!)

with best regards

Jim

Dr. Jim Cowburn G7NKS IO92ub

Biggleswade UK

Details on QRZ.com

August 19th 2017

Stefan DK7FC is busy again!

Hello VLF,

I un-wound the defective stack of the large coil which was used for 2970 Hz. It took about 4 hours to carefully unwound about 1000 turns, or about 1 km of wire. The wire will be used for new coils which are already planned.

Now, the remaining 4 stacks should hold at least 15 kV. I connected the coil to the antenna and found the resonance close to 4470 Hz.

Now i'm running (since 12 UTC) a carrier transmission on 4470.005 Hz. The antenna current is just 150 mA. That's an ERP of about 3 uW. A first signal on the 67 km band from here :-)

Let's see how long it holds until there is the next fault :-/

Reports/Spectrograms welcome...

As usual there is a monitoring of the signal in 3.5 km distance from my tree grabber: http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html

73, Stefan

August 12th 2017

Marcus reports:

It looks like we got a valid decode of Stefan's 16 hour transmission from the DL0AO cardioid antenna.

I had also attempted an early decode from a file ending 18:12 UT. This one appeared to be even better (rank 0, +2.2 dB carrier EbN0), perhaps because it ended before the QRN increased.

We had no success with the earlier 24 h transmissions on Aug 10th and 11th, neither single days nor both stacked - surely due to much higher QRN levels than today.

BTW Each decode attempt also produced several false hits with relatively good ranking, so a longer CRC might be preferable.

All the best,

Markus (DF6NM)

August 6th 2017

VLF,

After nearly 8 days the carrier is still on the air without an interruption, despite occasional thunderstorms :-)

It looks like the SNR is suffering by summer QRN, as expected.

The stable carrier was good for doing local tests with my Raspi+Octo-soundcard. The system is now completely configured including system time setting via the GPS module. I recorded a few days from the carrier, converted the data files into wav, reprocessed them in SpecLab: The carrier is stable and on the expected frequency, so the sample rate correction via vlfrx tools seems to work.

Forthermore i corrected some bugs in the circuit of my portable RX loop preamp for VLF (must have been late in the night when i built it up a few months ago). Now the noise is much lower. It looks promising! So it is time for a portable VLF experiment in the far field, just to check the system more seriously.

The crew of DL0AO has built up and optimised their VLF system to receive the weak 3675.005 Hz carrier in abt 220 km distance. Looks like there is something on their cardioidal spectrogram pointing to West,

http://df6nm.bplaced.net/dl0ao/VLFgrabber/vlfgrabber_dl0ao_test.htm

Something like 10 dB SNR in 31 uHz. That's not so bad!

I will run it for some more time until the trace is a bit longer. Then in some days i like to start transmitting an EbNaut message on that frequency which can be stacked until a decode appears. Markus has developed a tool for windows to do the stacking, maybe it works in that experiment... It will also be a test to see if i can decode the message from my own recording using vlfrx tools, an important step to pass...

So far so good. What are YOUR projects you are currently working on, LF/MF/VLF related?

73, Stefan

August 1st 2017

This is old news now but Stefan DK7FC has been busy on a new VLF band!

Hi VLF,

I'm back from LF for a while and built up my large VLF coil which was used on 2970 Hz in the beginning of the year. Actually it is under maintenance, one of the six stacks has to be replaced. It is already dismantled but the new wire is not yet wound on the 250 mm diameter PVC tube again.

So now the resonance is higher! I didn't know where it is and just connected the coil and scanned the frequency downwards. Near 3685 Hz i found a maximum of the antenna. Since the Q is not extremely high, i decided to tune to 3675 Hz and added the usual 5 mHz offset, to stay away from multiples of 1 Hz.

So, now since 14:40 UTC a carrier is running on 3675.005 Hz. The antenna current is 170 mA. I estimate the ERP is just 3 uW!

I guess this is a first amateur radio transmission on the 82 km band and that class of ERP (?).

Hopefully the coil will hold the 15.5 kV with just 5 stacks of windings. It's inductance is 3.9 H in the moment!

I intend to run the carrier for at least a few days, depending on the feedback.

Good luck for the VLF experts!

73, Stefan

PS: A 424 uHz RDF spectrogram is running at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html (First pixel appears in 30 minutes)

June 16th 2017

^{Stefan DK7FC has been busy on ULF again:}

^{Hello dear ULF friends,}

^{Here is my summary of the latest experiment on ULF which took place from 16...20 of May 2017. The experiment was to transmit for 90 hours on near 970 Hz, a wavelength of 309 km.}

^{The transmitter site was my normal inv-L antenna, 30m above ground, about 70m long. A modified HV mains transformer, driven by a homemade linear mode class-AB PA, produced 5 kV on the antenna wire. This results in 15 mA antenna current and an ERP of about 3 nW. The signals were generated by SpectrumLab software. The transmit signal was locked to a GPS reference.}

^{The receiver position was in JN49LN91GB, that's a distance of 27.2 km to the transmitter site. This is the path between TX and RX: http://no.nonsense.ee/qth/map.html?qth=JN49LN91GB&from=jn49ik00wd}

^{This time, an active E field antenna was used for reception because 27.2 km distance is still in the near field for that wavelength! It is about 55 % of the far field border distance.}

^{The signal was recorded by a Raspberry Pi running a USB stereo soundcard. The second channel was recording a reference signal containing PPS pulses and NMEA data from a NEO-6M GPS-module for compensating sample rate drift and sample losses. The data was written into a ~ 30 GB file on an USB stick connected to the Raspi.}

^{The data was post processed afterwards. Spectrograms in bandwidths of 424 uHz, 212 uHz, 106 uHz and 47 uHz were generated. A few optimisations were done to find suitable settings for a band pass filter and noise blanker.}

^{The first time, two EbNaut messages were transmitted, see the transmission plan:}

^{May, 16th:}

^{14:43:08 UTC: Start of recording. Carrier on 970.005 Hz for the rest of the day.}

^{May, 17th:}

^{Continuing of the carrier transmission, for the whole day.}

^{May, 18th:}

^{00:00:00 UTC: EbNaut, 5 characters, 16K21A, CRC4, 100 second symbols. Taking 24 hours exactly. The message was "DK7FC"}

^{May, 19th:}

^{00:00:00 UTC: Carrier on 970.01 Hz, for the whole day.}

^{May, 20th:}

^{00:00:00 UTC: EbNaut, 2 characters, 16K21A, CRC3, 60 second symbols. The message was "73".}

^{09:20:00 UTC: End of EbNaut transmission.}

^{10:27:05 UTC: End of recording.}

^{Here are all spectrograms and images: https://www.dropbox.com/sh/n7k0il4pp6vqbbc/AACbfwbN4TQ1RrS6YIEDYzMpa?dl=0}

^{The signal shows up to 15 dB in 47 uHz. There is no QRM in +- 10 Hz but the QRN was extreme, including local thunderstorms on the 19th. Several times there were lost samples into the recording but SpecLab corrected that nicely, so the spectrograms look as expected.}

^{Fortunately both EbNaut messages were decoded after a longer series of decode attempts. So there can be no doubt that this was a successful experiment.}

^{The next attempt will be to reach the far field border distance in > 49.3 km. I will need about 10 dB more radiated power, which is possible with some effort. Maybe an improvement on the receiver site will help to rise the SNR a bit more!}

^{73, Stefan/DK7FC}

June 3rd 2017

VLF tests continue by DK7FC:

Hi VLF,

Another one for tomorrow morning (this was June 3rd 2017):

f = 6470.100000 Hz

Start time: 03.Jun.2017 3:00:00 UTC

Symbol period: 24 s

Characters: 7

CRC bits: 5

Coding 16K21A

Duration: 7h, 8min, 48 sec

Antenna current: ~ 440 mA

73, Stefan

May 9th 2017

The exiting news is that VO1NA has been copied transatlantic on VLF. Joe was using 10uW ERP just above 8.7kHz.

April 25th 2017

DK7FC continues ULF experiments, whilst others continue experiments at VLF:

Dear friends of the Ultra Low Frequencies,

Yesterday a new experiment was done on the 309 km band. With the setup bescribed below, still running just 5 kV / 15 mA on 970 Hz, i crossed a distance of 14.4 km which is twice the distance of the last experiment. A plain carrier was sent on 970.005 Hz, at least this was the plan.

This is the location: http://no.nonsense.ee/qth/map.html?qth=JN49KL09AB

And this is the path: http://no.nonsense.ee/qth/map.html?qth=JN49KL09AB&from=jn49ik00wd

I recorded 196 minutes at 24000 kS/s starting 15:33:03 UTC.

As expected in the near field, the signal is much weaker than just 6 dB, rather 16 dB! But it is still there! A weak but doubtless trace in 3.8 mHz. The signal was peaking 18 dB SNR in 424 uHz.

There were some strange problems on the transmitter side. For the first recording hour there was no carrier. I had to walk 45 minutes to reach the next village to get some mobile internet to remotely restart the transmission. After 80 minutes the carrier disappeared again and came back 30 minutes later on 970.000 Hz. That was not intended but it acts a bit as a keyed carrier, a better ID which is well visible in 3.8 mHz.

It is very interesting just to listen to the recording (using a 6 kHz low pass filter). I like the sound of the sferics which are propagating well below 500 Hz, not only down to 4 kHz. It all helps to better understand propagation from DC to VLF. BTW there were many whistlers that evening and i catched many of them. It is a quiet location but i still think that the antenna has not the maximum possible sensitivity arround 1000 Hz.

Some pictures in the attachment (i still need to work out a comfortable dropbox alternative).

Now, that was the next step, 29 % of the far field border is crossed.

I'm planning a next experiment in 25 km distance, which would be 50% of the far field distance. Maybe i can do some QRO or i need to do a very long recording. The the current signal strength there should still be no problem in 47 uHz. This time i'm planning to use a larger E field antenna.

On the end of the 3.8 mHz spectrogram the signal became significantly stronger. Can there be some QSB, i.e. groundwave-skywave interaction even in 14.4 km distance? Or was it just constructive QRM/N? It will be interesting in the next (longer taking) experiment to see if there are some diurnal signal level changes. Maybe the band turns out to work much better during a certain time period...

73, Stefan

April 6th 2017

New world record for the 970Hz band by DK7FC

Hi ULF friends,

Saturday night i build an active E field receiver optimised for ULF. It is using a BF862 front-end as a source follower and a LT1028 with 20 dB gain. There are 3 RC filter stages cutting off at 10 kHz. Furthermore there are two isolation transformers in series, 4:1=>1:10. In the center they are parallel resonated. This gives a further good low pass filtering and some additional gain below 3 kHz. It was a quick construction without thinking to much, soldered at night, 02 AM local time. The antenna probe is a 1m long steel rod (for welding) with 2 mm diameter. The antenna height above ground was just 2m. There were no trees in a radius of 20 m.

For transmitting i'm again using the modified 5 kV mains transformer. At 970 Hz, the antenna impedance is 342 kOhm! So i can just run 15 mA antenna current which means 3 nW ERP. The new ALC build inside SpecLab holds the 15 mA accurately and protects the transformer that way! SpecLab is a very well usable tool for transmitting on VLF/ULF, thanks to DL4YHF!!

The transmit frequency was 970.005 Hz.

I didn't expect much, thought that this distance may be to optimistic. The last signals were very weak on my tree grabber in 3.5 km distance. But that tree grabber is using loop antennas and they are not sensitive in that frequency range. So there was a certain chance to see a trace, maybe in 212 uHz???

I drove to JN49JL00EB and built up the receiver there because it is a quiet location, a nice region for a walk and, there is a good restaurant not to far!!!!!! So it was easy to spend some time there and let the Raspi (using a GPS module on the right soundcard channel, with PPS+NMEA) record for nearly 3 hours at 24 kS/s.

This is the path between TX and RX: http://no.nonsense.ee/qth/map.html?qth=JN49JL00EB&from=jn49ik00wd A distance of 7.2 km, or 0.023 wavelengths or 14% of the distance to the far field border. So it is still a near field experiment.

It is about twice the distance i've managed in the last test.

Now i'm back in the shack, analysing the recording and to my surprise i can see a strong trace of 30 dB SNR in 424 uHz!!! See attachments in 424 uHz and 3.8 mHz.

All this makes me much more optimistic to reach farer distances. I tell you i will crack the far field border on that 309 km band! That would be a distance of 49.3 km.

There must have been some local thunderstorms not to far away, because there was QRN in the observed spectrum. So the SNR can be improved a bit by doing the next test in the late morning hours. Also the resonance of the transformers seem to be a bit to low, so maybe i can reach a bit more sensitivity when optimising that resonance. It could further help to rise the effective height of the antenna. Flat fields rather than the deep forest is the region to select now....

73, Stefan

March 29th 2017

By careful analysis over 9 days in 25uHz bandwidths, Paul Nicholson has proved beyond doubt that DK7FC was copied in Todmorden, UK on 2.97kHz. To think many believed we "wouldn't get over the garden fence" at VLF with amateur powers and antennas. Well done Paul and Stefan.

March 12th 2017

March 11th

"A quick report of very modest progress on this side of the pond --

the new coil is behaving itself quite well and is not arcing.

A low power test this afternoon yielded audible CW at 0.9km (!)

on 8277 Hz with a home brewed direct conversion rx and miniwhip.

It was a beautiful sunny day for a walk and strange looks from

motorists as roadside field experiments progressed.

The amazing Eu VLF results are inspiring and I hope to set a new

dx record (>lambda/2pi) and achieve a 20uW ERP eventually.

73 to all VLFers

Joe VO1NA"

March 2nd 2017

DK7FC's EbNaut messages have been widely copied around 8.27kHz. More experiments are likely.

Feb 22nd 2017

Hi all,

Hereby i'm announcing the next EbNaut attempt for a longer night transmission, starting in a few hours:

f = 8270.100000 Hz

Start time: 22.Feb.2017 18:00:00 UTC

Symbol period: 30 s

Characters: 8

CRC bits: 16

Coding 16K21A

Duration: 11h, 12m, 0s

Antenna current: 700 mA

73, Stefan

Feb 20th 2017

More success on 8.27kHz:

"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"

Feb 5th 2017

Successful message decode at over 3 wavelengths on the 101km band...

Hi Paul,

Am 25.01.2017 19:30, schrieb Paul Nicholson:

> f = 2970.000000 Hz

> Start time: 25.Jan.2017 07:00:00 UTC

> Symbol period: 30 s

> Characters: 5

> CRC bits: 16

> Coding 16K25A

Decoded at Bielefeld via DL4YHF (303.8km). Copied 'DK7FC' with

Eb/N0 +4.5 dB and constant reference phase.

S/N 19.1 dB in 29.8 uHz, -60.1 dB in 2.5kHz.

Just excellent! Thanks for working out the decode!

My call passed over 3 wavelengths on ULF, that's a dream! I am sure we will manage even more.

Very interesting to see the high Eb/N0 relative to yesterday. From the calculator it should have been weaker. And the QRN didn't look much lower than yesterday, at least from here.

Some there's a relatively high uncertainty down there, and the risk of getting no decode when coming to close to the limit. The stacking is an advantage again.

I'm still working on the recordings from the weekend. Gained a further

3dB by using very strong hum filtering, a threshold only 1.5 times the

mean amplitude and narrow notches. Enough to suppress not just the

harmonics but also the sidebands of the harmonics. Still no trace

here in Todmorden - yet. Still some permutations of polarisation

and azimuth to try.

Am 23.01.2017 18:52, schrieb Paul Nicholson:

Still no trace of the signal here. But tweaking the blanker

isn't going to go from 'no trace' to 'significant detection'.

3 dB is very significant! Congrats to that. It will also help to get better results from Renatos data. But as far as i remember he is offering the stream with the blanker already applied.

We could ask him to disable it temporarily, if that helps. If he knows what we're trying, he will do it i expect :-)

We are having fun with this! Constantly pushing at the limits.

Oh yes, and also a lot to learn about the optimisation work for the different bands.

73, Stefan

Jan 28th 2017

Quite a bit of activity from Germany on 8270Hz. Eddie G3ZJO is back monitoring.

Jan 23rd 2017

New distances on ULF!

Hello Wolf, Paul, ULF,

This is a most exiting result, 3 wavelengths on the 101 km band :-)

Thanks to Paul for extracting my signal from Wolf's stream. Thanks Wolfgang for providing the VLF/ULF RX system!

And congrats to our result, it is the first detection of an amateur generated RF signal on ULF over a distance greater than 1 wavelength! Also you are the first one except myselfe who picked up the signal!

I remember that 2970 Hz / 101 km story has started in summer 2016 and the first experiments were over quite short distances (3.5km, 7.9km, 17km (1st far field), 31km, 65km...) and was not seen as something that could be done over serious distances.

From now on i can say that it was worth to wind the large ULF coil having 6.1 H inductance, several thousand turns on a 0.25 m diameter tube, and > 5 kg of 0.4mm copper wire.

I am optimistic to pick up the signal from my recording in France, which would then also mean a first international detection of amateur generated ULF signals. The results will be there during the week...

73, Stefan

Hi ULF,

The postprocessing of my recording (0...12 kHz) from France is running. The first pixel of the 424 uHz spectrogram just appeared. It shows a peak on the right frequency having about 20 dB SNR! :-) See attachment.

The ongoing postprocessing can be followed at

http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/wide140.jpg

and

http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/424NMEA.jpg

Jan 20th 2017

More VLF/ULF activity:

VLF, ULF,

This weekend there will be some activity on VLF and ULF!

I'm running my next experiment on 2.97 kHz, my goal is to reach a 140 km distant location in France, JN38OO.

During that time (recording in F/ starting staurday arround 10 UTC) i'm recording the spectrum from 0...12 kHz with a loop pointing to 30/210 deg. It is a very quiet location.

I invited DF6NM and DJ8WX to transmit on 8270 Hz. I guess that Paul, SQ5BPF and RN3AUS as well as DF6NM and DK7FC are watching. Of course everyone is invited to transmit and receive. Transmit stations should announce their time/frequency here, to avoid any collisions. I am only transmitting on 2970 Hz and i expect there will be no one else.

My transmission plan is:

Friday, 20th:

8...17 UTC carrier on 2970.005 Hz at 150 mA antenna current.

Saturday, 21th:

8...17 UTC carrier on 2970.005 Hz at 150 mA antenna current.

17 UTC...8 UTC: DFCW-10800 on 2970.005- 2970.000_ Hz (each dash takes 3h, each break takes 1h). Message: 'F'

Between each break (20...21, 0...1, 4...5 UTC): EbNaut, 8K19A, 10s, CRC21, 1ch on 2970.000 Hz

Sunday, 22th:

8 UTC: End of the DFCW transmission

8UTC: EbNaut 8K19A, 32s, CRC16, 7ch on 2970.000 Hz

13:24:16 UTC: QRT.

More details soon...

73, Stefan

Jan 10th 2017

Stefan DK7FC tries even lower!

Hi ULF,

Since a few hours i'm running 15 mA antenna current on 970 Hz, the 309 km band. This requires to apply 5 kV to the antenna. You can see a very faint trace on the lower image at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html

Just about 10 dB SNR in 424 uHz in 3.5 km distance, or in 0.011 lambda distance. The receive antenna is a H field antenna that is not even pointing to the transmitter. Also the preamp noise is dominating the background noise on that frequency. So the RX is deaf on that band. Anyway, there is something.

The ALC into SpecLab does a very good job, it holds the antenna current stable during all the changes and working point drifts. The plot can be seen at http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/TX.png

15 mA results in an ERP of 3 nW.

My new preamp circuit is waiting for a first test together with the large loop. I hope to pick up the signal in at least 5 km distance with that preamp which is really low noise down to the lower Hz range.

An E field reeiver would be a better choise for the reception from that E field Tx antenna, at least in the lower near field. Maybe that will give another test then.

With 30 kV i could reach 0.3 uW. Not sure where this could be detected? And who knows the advantages of this part of the spectrum for our purposes!?!

Since 21:20 UTC, a 2 character EbNaut message is running. It will take 2h, 2min, 40s. Hopefully the tree grabber is available until the message ends. It will shut down in a few hours due to lack of solar energy in these days (an improvement of this system has already been prepared and waits for the installation).

73, Stefan

Jan 5th 2017

Stefan DK7FC continues his VLF work, this time at 5170Hz. Paul Nicholson in the UK has copied him, as has Marcus in Germany.