VLF Amateur News 2012



Please check either the RSGB's LF reflector email list or http://tech.groups.yahoo.com/group/sub9khz/ for latest news. Although I try to maintain this news page as soon as possible, there are times when I have been away or on holiday and unable to do so.


News from Italy of experiments at 8.97kHz experiments by IK7FMO

A year ago i started the first experiments in earth mode of 8970 Hz with variable oscillator laboratory. This autumn i start new experiment with a very stable oscillator in 8970 and exceeded 2 Km. in QRSS 10 with 100 Watt Amplifier. I hope, soon, to overcome the 8, 10 Km.

'73 de IK7FMO - Richard


There is news from Marcin SQ2BXI in Poland that his club station group is busy building at transmitter for 8.97kHz.

Marcin writes:

Hi All!

We’re building an 8,970kHz VLF transmitter at SP2KDS club.

We almost have everything in place:

What we still need is a generator to feed the transmitter. Required parameters are the following:

  • 8,970kHz frequency

  • regulating range +-0.05Hz

    • adjusting duty cycle of 5 to 45%, at 5% for two signals at the same time

  • two signals shifted by 180 degrees

A friend of mine has promised to build it but it’s been over a year now and nothing has happened.

Is there a software which would use a soundcard with the aforementioned parameters?

73! Marcin SQ2BXI


Piotr, SQ7MPJ, who was active on VLF TX last year, has died. He will be missed by members of the sub-9kHz community.


JT9 - a new digital mode for LF and MF (...and VLF?)

Hot news from Joe Taylor K1JT on the RSGB LF Yahoo group this evening about a new 9-FSK digital communications mode (for 2-way QSOs rather than beaconing) optimised for MF and LF bands. It could also be useful for VLF earth-mode.

"I invite you to try a new digital mode called JT9, designed especially for making amateur QSOs at MF and LF. JT9 uses the structured messages introduced in 2003 for the JT65 mode, now widely used for EME and for QRP operations at HF. JT9 can operate at signal levels as low as -27 dB (in a 2500 Hz reference bandwidth), with one-minute timed transmissions. It also offers slower transmissions of 2, 5, 10 and 30 minutes duration, and the slowest mode can decode signals as weak as -40 dB. With one-minute transmissions, submode JT9-1 has a total bandwidth of just 15.6 Hz -- less than one-tenth the bandwidth of a JT65A signal. The other submodes are narrower still: a JT9-30 signal occupies about 0.4 Hz total bandwidth.

Note that these JT9 sensitivity levels are comparable to or better than those of WSPR, which uses simpler messages and is not intended for making 2-way QSOs. JT9 has much higher throughput and reliability than QRSS CW, including DFCW modes.

JT9 is implemented in an experimental version of WSJT called WSJT-X. Some further details can be found at http://www.physics.princeton.edu/pulsar/K1JT/WSJT-X_Quick_Start_Guide.pdf , and an early version of WSJT-X can be downloaded from


Please note: WSJT-X is in an early development stage. A number of improvements and enhancements are already in the works, and others will surely be added.

Your feedback will be much appreciated!

-- 73, Joe, K1JT"


A LONG time period 32km test on 8.9775kHz

Starting late Saturday, G3XBM is repeating the VERY long carrier transmission using the earth-mode set-up to see if it can be detected beyond the normal earth-mode range. Transmission will be continuous (days long) so that G3WCD can see if the carrier seen a few days ago, when I was transmitting, reappears. If it does, I will drop carrier for up to a day before restarting the transmission. Chris G3WCD's grabber is at http://g3wcd.bplaced.net/ . Also monitoring may be G3ZJO. Any other suitably equipped stations locally are welcome to join. My QTH locator is JO02dg85VD in Burwell, East Cambridgeshire. Chris is 32km away from me.

UPDATE 26.10.12 Unfortunately, but not unexpectedly, the results were negative. One issue was the 13mHz drift of my TX over several days. Future long carrier tests will be done with a locked, very stable carrier which will keep the transmission within the very narrow FFT bandwidths used in 45uHz and 22uHz grabbers.


32km test on 8.9775kHz

Tomorrow evening, October 16th, at 5pm G3XBM is starting a 24 hour continuous carrier transmission on 8.9775kHz using the earth-probe "antenna" and 5W beacon TX. The carrier will be dropped for a few hours at some time (not previously disclosed) during the transmission to help later ID. Chris G3WCD, who is 32km to the west, is trying to see if anything at all is detectable at that distance. Realistically, success is very unlikely (the radiated power will be at pW or nW level), but with the ability to look in uHz bandwidths using Spectrum Lab it is worth a go.

If there is anyone else closer to Burwell, Cambs (JO02DG85VD) who wants to try looking that would be good.

UPDATE: No positive ID but just possibly a carrier detected? A much longer TX and RX time are needed to check this in 45uHz bandwidth.


G3XBM earth-mode tests

Successful QRSS3 tests at 8.978kHz today with the 5W earth-mode transmitter and 20m spaced electrodes. At 6km distance through the ground the signal was 10dB S/N in a 0.67Hz bandwidth. This is a considerable improvement over earlier attempts at the same test site, because the RX loop is now spot on tune (adjusted in the field using a capacitor switch box). The QRSS signal is visible in the image at 8.978kHz just above the strong wandering signal. With the S/N achieved using QRSS3 at this distance, WSPR should successfully decode.

An attempt will be made during this week to reach 7km, which would be a new personal best DX using earth-mode.

UPDATE 20.10.12

Several locations out to 7.5km were tried, but without success using QRSS60 (60 second dot period). This is a map showing where signals were received by 8.9755kHz earth-mode (through the ground) using 5W TX to 20m spaced earth probes at the transmitter.

Although work on radiated VLF experiments appears to have all but stopped in the UK and mainland Europe, G3XBM is about to restart earth-mode (through the ground) experiments at 8.97kHz. A new beacon has been built (see left) and several changes made to the receiving kit. The aim of these latest tests is to conclusively find out what makes a 5W CW/QRSS3 signal travel (at least) 6km when using a 20m spaced electrode pair at the TX end. Although some utilities assistance seems certain it is, as yet, far from clear how such signals get so far. With an inverse cube attenuation, signals should be far too weak to detect at this range. With a more stable TX signal and the beacon able to send a continuous carrier as well as 10wpm CW, QRSS3 and QRSS30 it is hoped that my current DX record with 5W can be exceeded. The last tests I did over a year ago with a 5W beacon resulted in 18dB S/N signals in a 45mHz bandwidth at 6km, suggesting that considerably further should be possible with a stable signal and narrower bandwidths.


There is a new VLF grabber at Darmstadt Germany that may be useful for 8.97kHz tests. It is at http://skmail.ikp.physik.tu-darmstadt.de/gvw/grabber.html. The grabber is primarliy there for VLF research into earthquake precursors.

Stefan DK7FC reports that the permit he has to use a 300m kite antenna expires soon, so he may try a further soon before that date.

Chris G3XIZ is still hoping to resume VLF tests once a new loading coil is wound.


Henny PA3CPM is again testing on VLF

Gm LF,





Henny PA3CPM is continuing VLF TX tests:

Gm LF,

The TX is on,8.970Khz ,

450 mA antenna current,

henny pa3cpm


best 73's


As I have been away in the last week or so I am well behind with VLF news - my apologies. Tests have been going on from several stations (DJ8WX, DK7FC, PA3CPM and others). A new VLF monitoring station is PA1SDB and Peter has been successfully receiving DJ8WX and PA3CPM on his E-field probe antenna (see results left). Peter has recorded his experiments at http://www.qsl.net/pa1sdb/.Stefan DK7FC has been considering further far-field tests using an earth electrode TX antenna with a long baseline (600-700m). Although ERPs will be much lower than with vertical Marconi style antennas, the advantage is that a huge loading coil is not needed and the system is essentially wideband allowing tests over a wide range of VLF frequencies to be tested with minimal TX changes. By using stable TX frequencies and very long carriers signals can still be detected at great range in bandwidths as narrow as 47uHz or smaller. This is a new area to explore for far-field experiments although earth electrode antennas have been used for earth mode tests over much shorter ranges for some years.


More activity from DJ8WX:

Hi all,

An hour or so ago the DJ8WX TX has been switched on.

QRG: 8970.022Hz


Speed: 3600 (means one sign = one hour)

Shift: 119mHz (sri, but I cant get it narrower programming an

EEPROM AT90S2313-10PC)

QRGs occupied: 8970.082Hz and 8969.963Hz.

So it shows the letter:

The TX will be on the air at least until tomorrow late afternoon when my XYL begins her garden work. Meanwhile she knows the PAs off-switch and she doesn’t hesitate using it disrespectful (when getting an electric shock). but today she is on shopping tour.



PA3CPM continues to test from time to time.


VLF Meeting and MFSK-37 experiment in Germany:

To my pleasure, the "original German VLF triumvirate", who held experimental 8.9 kHz licenses back in year 2000, are having a joint VLF / LF / MF meeting at my house this morning. Holger (DK8KW), Walter (DJ2LF), and myself (DF6NM) have just erected the antenna and are attempting a 6-letter MFSK-37 transmission. As before, we are using half-hour dashes with 1 mHz spacing above 8970.000 Hz, starting 9:00 UT.

Best 73,

Holger, Walter and Markus


Hardly in the super-DX class I know, but today G3XBM carried out his first earth mode tests this year on 8.971kHz using QRSS3. The purpose of the test was to try a new RX arrangement based on a 30t hi-Q loop feeding either the PA0RDT or G3XBM tuned drain E-field probes. Good signals were received at 1.6 and 3.5km range. Comparing results between both EFP/preamps, the G3XBM design gave slightly better copy. Using the E-field probes with a 19 inch whip gave no copy at all at either location.The picture shows the signal at 3.5km using a 5W Tx with 20m spaced earth electrodes at the TX end and RXing with the 30t loop and G3XBM preamp.30.3.12

Today comes the amazing news that Paul Nicholson in Todmorden UK managed to decode the complete MSK-37 VLF message exchange between DF6NM and OK3BVG a few days ago. Paul has a remarkably sensitive system but this result suggests that real message exchanges will be possible with optimised equipment between well equipped VLF amateur stations at decent DX distances.

Lubos, Markus,

I ran my recording from the 25th through an MFSK37 decoder program. It produced the following output:-

(asnr = amplitude S/N ratio)

vtcodec: 2012-03-25_07:30:00.000 rxed [N] asnr 2.87

vtcodec: 2012-03-25_08:00:00.000 rxed [B] asnr 2.63

vtcodec: 2012-03-25_09:00:00.000 rxed [B] asnr 3.84

vtcodec: 2012-03-25_09:30:00.000 rxed [N] asnr 3.68

vtcodec: 2012-03-25_10:00:00.000 rxed [M] asnr 4.46

vtcodec: 2012-03-25_11:00:00.000 rxed [R] asnr 4.51

vtcodec: 2012-03-25_11:30:00.000 rxed [O] asnr 4.30

vtcodec: 2012-03-25_12:30:00.000 rxed [R] asnr 3.81

vtcodec: 2012-03-25_13:00:00.000 rxed [T] asnr 2.21

vtcodec: 2012-03-25_13:30:00.000 rxed [U] asnr 2.21

The loops were aligned approximately 110 deg which was sufficient to reject another signal on 8970.022.


Paul Nicholson


Currently there is so much activity on 8.97kHz that it is hard to keep up! The RSGB LF reflector and the Sub-9kHz Yahoo group are the best places to keep informed "up to the minute", although I will post here too soon after.

PA3CPM is now being received well now he has more antenna current following a move of his loading coil outside.


First ever 2-way international amateur VLF QSO at 8.970kHz. Congratulations!

(click image on RHS for more detailed view)."Today between 7:30 and 14:00, Lubos OK2BVG and DF6NM successfully completed a two-way contact on 8.97 kHz. We believe that this is the first international QSO ever on VLF.

The distance between Breclav (JN88KS) and Nuernberg (JN59NJ 69es) is approximately 424 km. The weekend before, Lubos and I had found that we could see each other's VLF transmissions from our small home antennas in a slow spectrogram, using about 0.45 millihertz FFT resolution ("DFCW-6000"). This long integration requires about 2000 seconds of continuous non-interrupted carrier to reach full sensitivity.

We decided to use absolute frequency encoding of characters ("MFSK-37" mode), which has a simple structure but is significantly more efficient than two-frequency DFCW. The software signal generators in SpecLab were used to create 30 minute dashes by editing the frequency in 1 mHz steps every half hour. This can be automated by opening a textfile which is read by the "periodic actions" function. Between transmissions, additional half-hour gaps were inserted to let the FFT ring down, and allow for TX-RX reconnections.

Characters are identified by reading the frequencies above 8970.000 Hz, with 8970.000 to .009 assigned to the numbers, .010 idle or space, and .011 to .036 the letters A-Z. Lubos used a Rubidium standard to lock his transmit samplerate, while both receivers and my TX were synchronized by military MSK signals from GQD (22.1 kHz) and DHO (23.4 kHz).

With about 80 watts from an audio amplifier, I could get up to 0.38 A antenna current into my top-loaded vertical 9 m above the roof, radiating on the order of 10 to 15 microwatts. I believe that Lubos is using similar equipment, perhaps a couple of dB stronger. For receive, my soundcard was connected straight to the loading coil and antenna, whereas Lubos has an active probe at a quiet site remote from his TX location.

We wanted to go for a "full QSO" format with reports and confirmations, beyond the rudimentary three-dash "micro-QSO" format which was used in June 2009 between DJ2LF and myself. With single-letter suffixes, we ended up proceeding as follows:

07:30-08:30 "NB" ;Lubos' call: df6Nm de ok2Bvg

09:00-10:30 "BNM" ;my reply and report: Bvg Nm M

11:00-12:00 "RO" ;his confirmation and report

12:30-14:00 "RTU" ;my confirmation and thank you

Although today the noise was not as low as it had been before, we managed to exchange the essential information in 5.5 hours until 13 UT, after which QRN from lightning in southeast Europe became strong enough to obliterate further copy.

Attached image contains captures from Lubos' grabber at Apollons temple (top) and my receiver (bottom), with screenshots from the DK7FC and OE3GHB grabbers pasted inbetween. The original captures are at http://df6nm.bplaced.net/VLF/ok2bvg_df6nm_120325/. All spectrograms were stretched to the same timescale (5 min/pixel). On the left hand side, you can see a MFSK pre-test from Lubos, sending his call to hs own grabber at very low power. There was also a long dash from OE3GHB on 8970.030, and a carrier from DJ8WX on 8970.022 is visible at DK7FC.

The rightmost part of the captures shows the essential eight dashes from our QSO. You can see that I had almost lost Lubos' "B" when my noise blanker triggered heavily on local QRM, inducing me to give an "M" rather than "O" report. But hovering the cursor to 8:15 UT does show the peak at 8970.012 Hz in the spectrum graph. My final "R" is just barely visible at .028, whereas the following "TU" at .030 and .031 ended up drowning in the increasing noise.

During the lowest noise period (9 - 12 UT), the dashes were visible (though not decodable) in 4.5 mHz "600" spectrograms. At that time, our symbols also appeared on Paul Nicholson's spectrogram http://abelian.org/vlf/fbins.shtml#p=1332712800&b=110&s=sp

Thanks again to Lubos for the effort and patience! Although exchanging half-hour symbols is tedious and may sound boring to some, both of us enjoyed it and actually found it quite exciting.

Best 73,

Markus (DF6NM)"


VLF activity continues to be good at the moment with

transmissions during the last week from PA3CPM who is now putting a good signal on the G3ZJO grabbers (see right). Activity is expected from OE3GHB too this weekend, possibly others too.



OK2BVG has announced he will be active 18.3.12 so this weekend is a really busy one around 8.970kHz!

Hello VLF!

If the weather is as nice as today, I will be active on VLF tomorrow:

Date: 18.03.2012

Time: 08:00 UT - 11:00 UT

Antenna: Marconi L 24m up + 220m top load

PA: 120W

Identification: K

Mode: DFCW 3000

FRQ: 8970.040

Shift: 5mHz

I hope, the propagation will be good. All reports are welcome!

Lubos, OK2BVG


Belated news of PA3CPM's testing today


I am testing 8.970 Khz,constant carrier,I started on 10:30 Utc

power 60 Watt,antenne curent 2 Amp.

Henny pa3cpm



Eddie G3ZJO reports that 2 VLF stations were received at his grabber today:

Both stations received today OK2BVG around 3dB stronger than OE3GHB, both stations are running the same antenna current so Gerhard says he

needs to improve his TX antenna.

Both stations are still visible on my Grabber http://g3zjo.bplaced.net/index.htm in the 470uHz View OK2BVG at 8970.000kHz and OE3GHB at 8970.010kHz, the 47uHz view is just starting to show a nice white trace of both but merely a dot due to the 'short' periods of transmission.

Eddie G3ZJO

Mal G3KEV also reports clear traces from both stations in his DFCW600 window


News of a further planned test by OE3GHB on March 10th 2012

Dear group!

The weather forecast for tomorrow looks promising. Only weak wind to expect here. This gives me another chance to transmit on VLF tomorrow. If everything goes well, I will start around 800z.

I know this another short announcement but until about two hours ago it was unclear if I have to work tomorrow. Luckily I don't have to.....




OE3GHB has reported on his 8.97kHz VLF tests this weekend. He was copied by several stations in W.Europe. Gerhard's signal has been clearly detected by OK2BVG, DF6NM, DK7FC and by Paul Nicholson in Todmorden. http://abelian.org/vlf/fbins.shtml#p=1330855200&b=110&s=sp . There was a trace seen by G3ZJO. http://g3zjo.bplaced.com/index.htm

DK7FC have all been active in the last few days. Once again the 8.970kHz band has been buzzing with activity.17.3.12

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.

The picture shows Gerhard's set-up showing his loading coil (variometer) with integrated antenna current meter at the bottom left. In the background on the "table", the power supply, PC (locked to GPS) running SpectrumLab for signal generation. On the very right side is the Audio-PA. Input current was 15A (@13.8V) and the antenna current was close to 600mA. The antenna is his LF Station-Antenna. It is a 18m fibre pole with about 100m of horizontal top-load (~600pf)


OE3GHB has been testing on 8.97kHz in readiness for further tests tomorrow.

Dear group !

I plan to do a VLF-transmission tomorrow starting at approx. 8z.

The QRG will be slightly above 8970, most probably 8970,01.

I did some tests today to ensure everything is working as expected.

For sure you will see the result on my own grabber:


and at OK2BVG:




OK2BVG reports good signals from OE3GHB on 4.3.12


G3XBM gave a talk on VLF Amateur Radio to the Cambridge Radio Club (CDARC) this evening. There was a good turn-out and some interesting questions. See a copies of the slides by clicking the link.


DK7FC has started some tests with the weak signal mode WOLF on 8.97kHz. On Feb 2nd he reported first results on the LF reflector:


Yesterday in the night i tried some further tests on VLF, Dreamers-Band, 8970 Hz, using the WOLF 10 mode. An active E field probe was used on my home QTH which is 950 m distant to my work, where the fixed antenna (used for LF) was used to transmit on. That's not really a remarkable DX, not even in the far field. Anyway, it was fun and keeps me promising.

In contrast to the usual VLF work that is done from local fixed antennas, where "only" a few dashes are visible on the grabbers, i hope to cover some distance with this mode, where a full call and locator and something like 73, 55, CU, GL, TU... can be sent. In contrast to e.g. WSPR, what was reported to be about as "good" as QRSS-3 i want to give this mode a chance on VLF, as an exception. Maybe it helps me a bit to understand why so many LFers like the data modes, hi. ;-)

The receive site in the yesterdays test showed a quite good spectrum! To my surprise there is much less QRM at home. Here is a photo which shows the wideband situation during the test using the WOLF10 mode: http://dl.dropbox.com/u/19882028/VLF/Wideband%20at%20home%20in%203Hz%20FFT%20bin%20width.png

The TX was the LOPT driven by a more than suboptimal working class AB PA. The output voltage didn't really look like a sine wave but seemed to contain the wanted spectrum as well ;-) The PA took about 3 W input power and the PA efficiency must have been terrible. But the results were fine and so its worth (for me) to optimise things to gain at least 10 dB output power.

The signal wasn't visible in the WOLF gui spectrogram. Since its a spread spectrum it may not be useful to try to display it in QRSS-60 or slower.

The first decode appeared after about 6 minutes.

2012-02-01 23:26:43 >WOLF10 -r 22050 -f 8970 -t 0.3 -w 0.0000 -ut

23:27:07 f: 0.175 a:-0.9 dp: 73.4 ci: 3 cj: 66 LTEA6I*44POZVOC ?

23:27:31 f: 0.180 a:-1.1 dp: 69.2 ci: 4 cj:469 AESB3A64IHMY91V ?

23:28:19 f: 0.176 a:-0.9 dp: 66.5 ci: 0 cj:348 XETAVDCFKFJ/6ZL ?

23:29:55 f: 0.273 pm:1.216 jm:407 q:-13.2 -8.6 TFVIM68HW6GXMMB ?

23:31:31 f:-0.127 pm:2.044 jm:741 q: -5.4 -6.2 71DU8HVLDJN49IK -

23:33:07 f:-0.127 pm:3.457 jm:741 q: -4.3 -5.2 73 DK7FC JN49IK -

23:34:43 f:-0.127 pm:5.364 jm:741 q: -3.0 -3.5 73 DK7FC JN49IK -

23:36:19 f:-0.127 pm:5.745 jm:741 q: -1.8 -2.3 73 DK7FC JN49IK -

23:37:55 f:-0.127 pm:6.250 jm:741 q: -0.9 -1.6 73 DK7FC JN49IK -

23:39:31 f:-0.127 pm:7.205 jm:741 q: -0.2 -1.3 73 DK7FC JN49IK -

Then i've done several tests using different frequency tolerance values (above: t = 0.3 Hz). After calibrating the soundcard by using the shown offset, the offset was 0, consequencial ;-) But even if a tolerance of 0.002 Hz was choosen, it still took about the same time to get the first decode. Any comments?

2012-02-02 01:33:16 >WOLF10 -r 22050.222 -f 8970 -t 0.002 -w 0.0000 -ut

01:33:40 f: 0.005 a: 1.6 dp: 70.7 ci: 3 cj:391 U3K6J06JK76C6J0 ?

01:34:04 f: 0.002 a:-1.5 dp: 67.0 ci: 2 cj:395 0V*9CNF9T3VME9V ?

01:34:52 f:-0.001 a:-1.4 dp: 62.8 ci:13 cj:151 N9KZRESEV9.EUHJ -

01:36:28 f: 0.000 pm:1.159 jm:659 q: -6.8 -8.5 3DZ037H*TFCZL10 ?

01:38:04 f: 0.000 pm:2.101 jm:659 q: -4.7 -5.1 73 DK7FC JN49IK -

01:39:40 f: 0.000 pm:2.699 jm:659 q: -5.1 -3.8 73 DK7FC JN49IK -

01:41:16 f: 0.000 pm:3.896 jm:659 q: -3.4 -2.4 73 DK7FC JN49IK -

Currently the PA has problems with self oscillations that even seem to be present when there is a input signal. But sometimes the self oscillations were OFF. During this time the signal was visible in the spectrogram. So i am optimistic to cover much more distance as soon as the PA works as intended.

I want to ask the experts which S/N imrpovements can be expected when using the WOLF 5 or WOLF 2.5 mode? Is it 3 dB respectively 6 dB?

Right now i feeld that i am missing a spectrogram which i can show here. Just text! Odd.

73, Stefan/DK7FC


Activity from DJ8WX again:

Hi all,

Sri for my being AWOL. I have been busy on shorter waves making some HST tests. Since some days my VLF stn is on the air agn.

QRG: 8970.022Hz or 8970.000Hz

Time: afternoon and evening

The Todmorden Grabber shows the ZOA times. the OK2BVG grabber shows the signs sometimes. The sign on 8970.000Hz is 0.05% amplitude modulated with 1PPS. pse see: http://dj8wx-dl.de/GPS%2013.01.2012best regards Uwe/dj8wx/jo43sv

G3ZJO managed to copy Uwe's VLF signal in 42uHz bandwidth. This is the screenshot from Spectrum Lab. He was also visible in 424uHz bandwidth but far less clearly. I was unable to look myself, but signal levels look lower than I recall when DJ8WX was testing last year.