December 14th 2019
Quite a bit of activity recently including some constant carrier tests with earth-electrode antennas and 100W from Brittany by Jean-Marie Polard F5VLB. I have not sound out if he was detected at great range. It is very close to 8.27kHz and GPS locked.
November 24th 2019
VO1NA has been decoded on sub-9kHz in Europe.
See https://groups.io/g/rsgb-lf-group/topic/vlf_vo1na_8270_0075_hz/61873847?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,61873847
November 16th 2019
For latest news of sub-9kHz experiments please see https://groups.io/g/rsgb-lf-group .
October 1st 2019
Unless I have missed something (entirely possible!) last month was quite quiet on VLF for amateurs.
August 20th 2019
It seems ages since this was last updated. Stefan DK7FC reports that the Alpha beacons are back.
May 15th 2019
I have NOT included Stefan's attachment.
Hello SLF freinds,
Just a note from a recent experiment at 270.1 Hz.
On sunday morning, 2019-05-12_10:34,+150m, i've done a carrier transmission on my ground loop antenna again. I did not expect more than, hopefully, a detectable spectrum peak in 57.6 km distance, i.e. at my tree site. The tree receiver site was listening and recording data using vlf-rx tools.
One E field antenna and two orthogonal loops were listening. The loops have been improved recently! They consist out of a single circular turn of 1.2 m diameter using 10mm diameter copper tube (about 25 mm^2). It is a closed loop, non-resonated, with an impedance matching transformer. This transformer previously had 1:100 turns. Now it (they) has 2:240 turns, i.e. two turns primary (out of 14mm^2, AWG6). This improved the sensitivity below 2 kHz significantly ( abt. 4...5 dB).
Furthermore the TX antenna length and angle has been improved, resulting in about +3 dB more signal strength on the RX site!
In a previous experiment at 270.1 Hz, some month ago, there was no result at all, not the weakest trace, despite excessive tweaking of all parameters. So the question was, will the improvements result in a detectable signal now?
Several things went wrong in that experiment. I forgot a bag containing important equipment such as the power supply for the netbook that generates the carrier signal. Also the output power was not as high as planned, just about 380 W, giving 2.2 A antenna current (I measured 64.7 V at 1 A DC). Anyway i managed to improvise so the experiment was started, but with some hours of delay which meant i higher QRN background level. Then, on the WLAN link to the tree, there were several interruptions of the stream (i'll move to 5 GHz very soon!). I even got some QRM from my battery charger for some short time periods (forgot to disable the charger remotely). So there were several factors that could have been improved or avoided. And the middle of May is not the ideal time anyway.
Well, 270.1 Hz, that's the 1110 km band! The far field begins at 177 km distance, i.e. i am clearly in the near field here. Thus, from a 'magnetic' TX antenna, we would expect that the signal is mainly detectable on the H field, i.e. the loop antennas.
The first interesting results is that this expection is actually confirmed. There is nothing detectable on the E field but the carrier S/N in the H fields is close to 10 dB in the first run. Mixing the H fields and tweaking the filters rises the carrier S/N to 10.7 dB, see attachment.
So far not really an undoubtly detection but it is a candidate for optimism! With a few less problems during the experiment there is a chance for 14 dB SNR. Also, there is quite much sideband QRM arround 300 Hz which makes 270 Hz a bit harder to work on.
73, Stefan
May 6th 2019
Rather too late, but better late than never! These messages were posted recently:
DL0AO is currently observing E- and H-fields around 1670.1 Hz:
424 uHz: https://vlf.u01.de/VLFgrabber/vlf5.jpg
Fieldstrength plot: https://vlf.u01.de/VLFgrabber/vlf5.png
106 uHz: https://vlf.u01.de/VLFgrabber/vlf9.jpg
DF9RB is also watching with his new dipole antenna.
73 and good luck,
Markus
-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group@blacksheep.org <rsgb_lf_group@blacksheep.org>; Renato Romero <contact@vlf.it>
Verschickt: Sa, 4. Mai 2019 19:04
Betreff: ULF: Carrier transmission announcement, tonite
Hello ULF friends,
It's time to do a ULF transmission again. Hopefully the QRN will stay low tonite. I'm planning to transmit near 1.67 kHz, which is lambda/2 for the distance between earth and ionosphere at night. With some luck we can get some gain from that resonator, like the tweaks do?
Exact start time, power, and antenna current will be mentioned later. I think the transmission will start arround 21 UTC.
Hopefully the QRN will stay reasonable low. It is certainly not the best time in the year, but anyway.
Reports welcome! :-)
73, Stefan
April 13th 2019
This appeared on Facebook on April 7th. It was posted by Paul Nicholson:
Last night Stefan DK7FC drove into the forest taking with him a large amplifier and a very large battery. These he connected to a pre-installed 1130 metre ground loop antenna. The amplifier was fired up at 487W to put 2.44A at 2970.1Hz through the loop. For 2 hours he transmitted a 7 character EbNaut (coherent BPSK) message from a GPS locked signal generator.
Paul also wrote:
Stefan's transmission was also decoded in Italy via the online VLF receiver run by Renato Romero IK1QFK, a distance of 490km. Eb/N0 was +0.1dB with the great circle path 54 degrees off the plane of the transmit loop. The received signal was 57dB below noise in a 2.5kHz audio bandwidth, about 15dB below noise in the 167mHz bandwidth of the transmission.
And (April 12th 2019):
After much computing effort by Jacek Lipkowski SQ5BPF, Stefan's 2970.1 Hz message sent on 6th April was successfully decoded from well beneath the noise in Warsaw, 975km away - a new amateur radio distance record at ULF. Eb/N0 was -0.4dB.
March 28th 2019
Stefan is thinking of doing a staircase experiment to find out the optimum frequency for a 2-way VLF QSO.
Hi VLF,
Yesterday there was a sudden transmission at 14.5 kHz, coming from the
west. Today, there was a VLF staircase beginning at 12 kHz upwards,
coming from the east... ;-)
After the recent successful experiment at 5170 Hz, with very high SNR
levels in a short time received at DL0AO and Paul, i already discussed a
bit with Markus about a VLF staircase that could be transmitted from 8.3
kHz downwards. It seems we are able to characterise propagation of a
ground loop antenna. It would be interesting to find 'the best'
frequency for a QSO attempt over the path between TX and RX stations.
This will of course differ with daytime and locations.
For frequencies between 8.3 and 5 kHz it looks like a short carrier of
<= 5 minutes will be sufficient to produce a strong enough signal peak
(SNR >= 14 dB). Thus i could transmit for e.g. 5 minutes in frequency
steps of 200 Hz beginning at 8.3 kHz. The experiment could be repeated
at night, to see the difference. And another one could be done at lower
frequencies, e.g. starting at 5 kHz downwards, using longer carrier
intervals.
Especially the range below 4 kHz could be interesting. Thinking back to
the experiment between me and Paul, at 2.97 kHz, we have always been
uncertain if propagation could be 6 dB better when moving by 100 ...200
Hz. Now we may be able to analyse that.
The experiment could be done in a reasonable short time, so that
propagation doesn't change to much during the experiment. Also, i can
tune the antenna within less than 5 seconds to a new frequency. Using
SpectrumLab, a pre-arranged frequency list schedule could be worked out,
so QSY happens precisely timed.
Markus and i were thinking about a kite / ground-loop VLF QSO with 15
character messages in 15 minute intervals. In the past it turned out
that 5170 Hz is a very useful frequency for a QSO over a distance of ~
200 km, even better than 8270 Hz, at least in daytime, because the QRN
begins to drop in that frequency range in daytime and skywave-groundwave
interfering effect seem to be constructive.
Are there ideas for a better way to characterise propagation?
Maybe a newcomer is interested to take part? Now it is the chance for a
new project :-) Forget the summer hole.
73, Stefan
March 13th 2019
It seems that Stefan DK7FC is breaking yet new ground. This message was posted 8 days ago.
Hi ELF friends,
During the last 2 weeks i've done another experiment on ELF, this time
on 12.47 Hz, the 24 Mm band (wavelength 24057 km). Again i've crossed
the local distance of 3.5 km. That's the lowest frequency i've ever been
and it feels like i can see the ground already :-)
The dimensions of everything down there are extreme. I've integrated 227
hours of a carrier transmission into one spectrum peak, it is shown in
the attachment in 1.25 uHz. This carrier could have transferred an
EbNaut message of nearly 100 characters.
The ERP was 50 attowatt or -163 dBW and the antenna current was 170 uA
only, despite about 5 kV antenna voltage.
I'm now trying to put a step below 10 Hz but the RX antenna becomes less
efficient with each Hz.
73, Stefan
March 7th 2019
This was on Facebook earlier from Paul Nicholson:
The combined efforts of Marcin SQ2BXI and Jacek SQ5BPF last weekend led to the first amateur VLF transmission out of Poland and also the longest known distance for an earth dipole (ground loop) transmitting antenna at VLF. With 100W to a 500 metre earth dipole their 8270Hz signal was clearly detected in England at 1343km distance and a 2 character EbNaut message was decoded.
The experiment was carried out under the banner of their wonderfully named Klub Niezwykłych Łączności, see the full write-up at https://klubnl.pl/…/nadawcze-proby-z-dipolem-ziemnym-w-zak…/
Feb 26th 2019
Stefan DK7FC has been busy on 470.1Hz. His ULF signal has been detected at 57.6km.
Feb 26th 2019
Riccardo IW4DXW has been transmitting on 8.27003kHz and has been copied in Germany.
Feb 10th 2019
From France Jean-Marie F5VLB is gearing up to do some VLF earth mode tests with a 150W GPS locked TX and a 25m baseline. With a very long transmission, he might be detectable by radiated signal by the better equipped stations.
Feb 9th 2019
He's been at it again! Stefan DK7FC was transmitting on 22.97Hz a few days ago. As far as I know, this is the lowest ever frequency transmitted by an amateur.
Hi ELF ;-)
I'm glad to announce that since 15:46 UTC i am transmitting on ELF (the real ELF, i.e. into the range of 3...30 Hz, ITU radio band 1 ) for the first time ever.
Here are the parameters:
TX frequency: 22.970 Hz
Wavelength of that frequency: 13060 km
Antenna voltage: 4.8 kV rms (+ a DC component of 7.5 kV)
Antenna current: 325 uA
ERP: 600 aW, or 6E-16 W
Call it QRP!
The goal is to detect the signal on my 3.5 km distant tree grabber, whose E field is now working again. Since the E field probe is not to far above the tree, the effective height is not as much as it should ideally be, at this frequency, so the RX is somewhat deaf. Anyway i can see the Schumann resonances and the 60 Hz power grid. So i hope it will work.
A spectrogram which is centered on the frequency of interest in now shown at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html (3rd window). But maybe 424 uHz FFT bin width is even to optimistic! In a few minutes we'll see more :-) It takes about 40 minutes until a peak could have fully developed...
73, Stefan
Later he wrote:
...wow, after analysing the first 90 minutes of the transmission I found that the best SNR is achieved without sferic blanking! So then the hum filter and the low pass filter can be disabled too.
So far, during that noisy evening period, i'm getting about 14 dBSNR in 185 uHz.
Unfortunately i temporarely overloaded the PC while doing the analysis,which caused an interruption of the stream and then all SpecLab instances did a restart.
Now the spectrogram is generated from the unfiltered and unblanked stream and now we can already see a clear peak right on the expected frequency, showing about 10 dB SNR.
I intend to run the carrier at least for 24 hours, if all works well.Not sure if and how the antenna current will drop when it starts to rain. It would have been better to decouple the DC component from the antenna by using a big series capacitor but id didn't have one that holds 20 kV or so.
More later...
73, Stefan
Jan 21st 2019
As in earlier years, Stefan DK7FC has been busy at VLF. In recent days he has been doing tests around 8.27kHz.
Also active has been Joe VO1AA on 8.2700075kHz.