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Klub Niezwykłych Łączności
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    Christmas  transmission from SAQ on 17.2kHz, 24 december 2018 8:00 UTC

    Received at SQ5BPF QTH Warsaw/Poland KO02md.

    E-field active antenna, vlfrx-tools and Spectrum Lab receiver

    The message was:


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    Since a few days one can see a faint line on 8270.0075Hz. This is transmitted by Joe VO1NA from Canada. The distance to Warsaw is 5100km!

    Spectrogram with normalized amplitude:

    I have received Joe VO1NA in 2017 when he transmitted ebnaut:


    You can also see a very strong signal from Stefan DK7FC on 8270.0Hz


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  • 12/26/18--14:54: 8270Hz pileup
  • We are starting to have pileups in the 8270Hz band, you can see this on our grabber:

    Joe VO1NA on 8270.0075Hz , Stefan DK7FC on 8270.0Hz, Uwe DJ8WX on 8269.996Hz. And maybe Riccardo IW4DXW on 8270.003Hz

    8270Hz pileup

    Spectrogram with average amplitude normalisation, but without annotations:

    Spectrogram without amplitude normalisation:


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    Stefan DK7FC did a succesful transmit experiment utilising a ground diole on VLF. This resulted in a really strong signal on our Warsaw grabber (over 900km distance):

    The spectrum after amplitude normalizastion:

    The antenna had about 900m and the current was about 1A. A full descrption is avaliable in the  rsgb-lf-group list archives:


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  • 02/08/19--23:28: End of NDB BIA on 474kHz
  • Sadly the NDB BIA on 474kHz in service at Rzeszów Airport has been turned off.

    For many years the carrier at 474kHz and the sidebands at 473kHz and 475kHz were used by polish radioamateurs to check their 630m equipment. Foreign radioamateurs used this NDB to judge the propagation to Poland.

    This will change the way we work in the CW segment in the 630m band in Europe. Up to now we had to use 472-472.7kHz or around 473.5kHz, and a narrow filter was necessary. After BIA is switched off we can use the whole 472-475kHz segment, also with wider filters.

    NDB BIA 474kHz antenna

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    The RSGB LF Reflector is the most important group for low-frequency enthusiasts. For many years list members have been witnesses to milestones in the 136kHz, 73kHz, 500kHz, 472kHz, VLF and lower bands. Many posts have great historical significance.

    When we created the KLUBNL.PL website, one of our most important goals was to create a publicly available archive of this list:

    In the beginning this archive spanned from 2014 up to now. Recently we imported archives kindly donated by Dave G3YXM and Markus DF6NM. Thanks to them the archive now spans from February 1999. 20 years of radioamateur longwave (and medium-wave) radio history!



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    Encouraged by our last experiments with ground dipoles we decided to do a transmit experiment with this antenna on VLF 8.270kHz, 36km (36000m) wavelength. Thanks to  Fab LAB Trójmiasto we had a great location on the see on a cliff near the Baltic Sea in Gdynia. Our goals for this experiment were:

    • Try transmitting from a ground dipole on VLF
    • Assess the field strength near the sea
    • See if it is possible to reach greater distances with relatively simple equipment and low power.
    • Test a broadband transformer for VLF-LF-MF

    1. Location

    We had a great location on a cliff in the Kolibowski Park near the Gdańsk Bay, and hoped that the ground water level would be low (increasing the ground loop area). We could also use two water bodies for grounding: a nearby lake an the Baltic Sea.


    The antenna length was about 500m. The antenna was grounded a small local lake (using a 1m long aluminum profile) and the Baltic Sea (10m of wire sunk in the Gdańsk Bay). For the antenna wire we used a copper-coated steel welding wire of about 1.2mm circumference (160m) and 0.8mm (the rest of the length). It was not the best material available, but we used it because of low cost. Where possible the wire was strung high in woods and bushes.

    A beautiful sight from one of the antenna ends

    The other end of the antenna

    The antenna parameters were:

    • Antenna voltage at the feed point: 300V
    • Antenna impedance at 8.27kHz: about 1200Ω
    • Resistance measured ad DC: about 500Ω
    • Calculated DC resistance of the antenna wire: around 140Ω
    • Transmitter power: around 75W
    • The radiated power is probably well below 1 uW (0,000001W)


    – GPS synchronized generator

    – A generator based on an old terminal; with an x86 processor, which had a uBlox Neo-7m GPS installed inside. The GPS is connected to the terminal serial port for control, and to use the GPS output for a coarse time reference (this is not very precise because the 1PPS signal is not connected). A 20kHz signal from the gps is connected to the sound card in the terminal and is used as a reference for Paul Nicholson’s excellent ebsynth Linux DDS and modulator

    This enabled us not only to generate a carrier, but also to transmit ebnaut

    • old Polkat Forte 201 public address amplifier

    This amplifier has been modified a bit. More output transformer taps were made available on the back connector. Forced cooling with two computer fans was added to enable continuous work at high power.

    • An autotransformer for 8,27kHz-479kHz.

    Uniwersalny nadawczy autotransformator antenowy na pasma 8,27kHz, 136kHz i 472kHz.

    1. Results:

    -The signal was received by Paul Nicholson at a distance of 1342km. As far as we know this is the first international reception of an amateur generated VLF signal from Poland. We transmitted “SP” (which is the prefix for polish stations) using the EbNaut mode on 8270.00073Hz.

    From 20190302 11:30 UTC to 20190303 04:00 UTC we transmitted a carrier on 8270.005Hz. This was visible on Paul Nicholson’s grabber:,147,688,173,1

    Our signal received at 1342km distance

    -We measured the magnetic component of the field using a 90cm diameter loop antenna. The signal was visible at about 6km distance even with a fast FFT. At first we used  131072 FFT size with 48kHz sample rate: 370mHz per FFT bin, 2.7s FFT window time, later we added 32x decimation, which gave 11mHz per FFT bin, 1.5min FFT window time.

    -The reception was better over high conductivity terrain. For example reception was better over a river than a shirt distance from it.

    -The experiment showed that it’s possible toget positive results from cheap and simple amateur equipment.

    -The ferrite ring autotransformer has proven itself. It was cold even during continuous power for long periods of time.

    1. The experiment was done by:

    -Marcin SQ2BXI

    -Jacek SQ5BPF

    -Julian (no callsign yet)

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    Recently we’ve done a successful  transmission from an earth dipole on 8270 Hz.

    This is the first amateur transmission on VLF from Poland which has been received in another country. This is also the record distance for a transmission using a ground dipole antenna – over 1330 km.

    Link to Paul Nicholson’s post about it:

    Link to Paul’s VLF milestones list:

    This is probably the first VLF signal which has been transmitted from Poland after World War II. We are not aware of any military or other transmissions. Before the war we had the Babice Transatlantic Radiostation (callsigns AXO/AXL/SPO/SPL), which was similar to Grimeton/SAQ.

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  • 04/11/19--12:40: ULF 2970.1 reception record
  • Stefan DK7FC transmitted at 6 aptil 2019 20:25 UTC at 2970.1Hz. The TX power was 487W into a 1130m ground dipole antenna. The ebnaut transmission parameters were:

    f = 2970.1 Hz
    Start time: 06.APR.2019 20:25:00.3 UTC
    Symbol period: 6 s
    Characters: 7
    CRC bits: 16
    Coding 16K21A
    Antenna current: 2.4 A
    Duration: 02:04:48 [hh:mm:ss]

    The signal was received by Jacek / SQ5BPF in Warsaw/ Poland KO02md, at a distance of 976km!

    After the filtering and noise blanking was optimised, the signal could be decoded:

    sq5bpf@jitter:/stuff2/sq5bpf/vlf_stefan2$ vtcat -p  ../vlf_stefan2/pliktmp6
    sq5bpf@jitter:/stuff2/sq5bpf/vlf_stefan2$ vtblank -v -d0.0007 -a20 -t 50 DK7FC/P]
    carrier phase: -10.6 deg
    carrier Eb/N0: -0.4 dB
    carrier Es/N0: -15.33 dB
    carrier S/N: 15.63 dB in 133.5 uHz, -23.11 dB in 1Hz, -57.09 dB in 2.5kHz
    elapsed 92

    The message was: DK7FC/P

    Link to Stefan’s email:


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    SAQ transmision on Alexanderson Day, June 30th, 2019:

    10.30 (08.30 UTC) Alternator is started
    11.00 (09.00 UTC) Transmission of a message

    13.30 (11.30 UTC) Alternator is started
    14.00 (12.00 UTC) Transmission of a message

    More info:

    Welcome to Alexanderson Day, June 30th, 2019