Pages

Friday, November 28, 2025

Digital Amateur TV experiment between Belgium and Greece on the 29 MHz band - Nov 2025


Radio amateurs have been sending and receiving TV signals for a number of decades. First it was analogue TV and that became digital TV in more recent years.

With the advent of digital TV or digital amateur TV (DATV) to give it its full title, radio amateurs have been resourceful in squeezing video signals in smaller and smaller bandwidths. This has resulted in signals being several hundred kHz wide instead of several MHz.

During tests on 29.400 MHz in November of 2025, Stavros SV1EBS in Athens, Greece managed to receive the DATV signals from Frans, ON4VVV in Belgium, a distance of about 2124 kms.

The path which was most likely via a single F2 layer hop off the ionosphere was the first reception of a DATV signal from Belgium in Greece.

The image above contains some screenshots of the signal from ON4VVV. The image below is a screenshot from the YouTube video from SV1EBS. It shows the MiniToune software and I have highlighted the received signal from ON4VVV in red.


Technical details... For this experiment, ON4VVV was using a homemade Portsdown TX with a mini Lime SDR and a Rasberry Pi to generate the D-ATV signals. The format used was DVB-S2 with a symbol rate of 125 kilo-symbols per second (125 kS/s) with Forward Error Correction (FEC) of a ½. The data rate was 250 kilobits/sec.

The D-ATV signal bandwidth on 29.4 MHz was about 150 kHz and Frans was running 400-watts from a homemade power amplifier to a 4-element mono-band beam at 19 metres above ground level.

On the receive side, SV1EBS in Athens was using a simple dipole for 10m with an upconverter in front of his “minitiouner”. It's worth noting that this basic set up resulted in a successful reception of the D-ATV signals. There is plenty of scope for improvements with the addition of a directional beam with gain, a pre-amplifier and a bandpass filter.

Frans, ON4VVV writes... "This signal was demodulated by the minitiouner into a colour picture with strength indicator between D1 and D4. This means that he had between 1 and 4 dB of spare power in RX.  

A second test was done with DVB-S2 and symbol rate of 250 kS/s and this was  demodulated into a picture for only a short time."

The video clip below is from SV1EBS which shows reception of the D-ATV signal on the 9th of November 2025. Note that the test card that is being received is video and not a single static image.

Second test on the 16th of November... One week later, some more tests were carried out and the signals were even stronger. 

Fran writes... "Exactly one week later we did the same test in DVB-S2 with SR 125ks and FEC ½ because maybe we had been simply lucky that first time. Again SV1EBS could demodulate my signal but this time up to D8 meaning a real strong signal with up to 8dB spare RX signal

We decided to switch over to SR 250ks with my camera connected and again it produced a picture , but this time a moving picture from my camera. Both connections have been demodulated during tens of minutes."

A video of the second test can be seen below...

Analysis... While this may seem at first to be just the reception of a low resolution video, it's a significant achievement.

First, there is the challenge of reducing the bandwidth of a video signal from MHz to just 150 kHz and the guys in the ATV community have been doing this successfully. The second part is the challenge of trying to receive a D-ATV signal off the ionosphere.

When you listen to someone on a narrow band mode like SSB, you can hear the audio and the signal strength changes over time i.e. there's fading. This is often due to the signal arriving in phase and out of phase as it comes back down off different parts of the ionosphere. In other words, the path length is changing.

When you look at a D-ATV signal coming from someone a few kms away, you'd see a nice clean signal on the waterfall display. When the D-ATV signals comes down off the ionosphere, it looks something like this...


The dark diagonal streaks are where the signal is being cancelled out. It starts at the higher frequency and as the conditions change over time, the 'notch' moves lower in frequency as the longer wavelength signals cancel out.

As you might imagine, losing big chunks of the digital video signal plays havoc with reception.

Future tests... ON4VVV is looking trying for a trans-Atlantic reception report. Frans writes... "I am sure that transmitting D-ATV from EU to USA must be possible and demodulated into a moving picture too, but all my efforts to find somebody over there with a decent antenna to receive me was in vain."

Anyone in the USA or Canada interested now that we're still near the peak of the sunspot cycle and conditions on 10m are still good?

Links...

1) Previous report about a successful DATV test on 29 MHz across the North Atlantic - 7th Nov 2022

2) More information about the proposed Amateur TV experiments at 29.250 MHz & 51.7 MHz 

12 comments:

  1. How extraordinary! That second video where you see Frans waving, in 150 kHz, at that distance, wow.

    ReplyDelete
  2. I'll leave a video of my reception at location KN95BG, which is about 2,600 km from the signal source in Belgium. On November 29th, I tested speeds of 33, 66, 125, and 250 kbps. I received all of these modes. But why didn't I receive audio in these broadcasts? Was it there, or is the problem a lack of a codec on my PC?
    73!
    KarapuZ
    https://rutube.ru/video/private/02c17478e0d3bde7127eb843829fdbab/?p=LRxhTDEASKOmdNtk6mQLjg

    ReplyDelete
    Replies
    1. Dear KarapuZ, thank you for the very interesting video. I had switched off the sound of my D-ATV in order to save space for the video, however you can see me talking with Stavros SV1EBS on an ATV ZELLO channel : "ATV Belgiƫ".
      My 4el antenna does not have a very narrow beam but anyway the difference in direction must have been more than 25°. Please let me know your RX setup, very interesting.
      73's Frans ON4VVV

      Delete
  3. Dear Frans, I don't have much to describe. The receiving setup is simple – in this case, it was an Inv. V 2x20 m antenna, with the feed point at a height of ~16 meters and its arms facing southwest. The Elad S2 receiver, which on November 29th recorded IQ data in a 6 MHz wide band with a center frequency of 29 MHz, was used. This was done intentionally, as I intuitively assumed that your D-ATV tests, which I first received on November 16, 2025, would continue due to good propagation in this frequency band. Frankly, I was extremely surprised when I first saw such "wide" signals in the upper HF bands.
    I hope nature will be kind to your tests in the future, although the maximum of this solar cycle will likely soon begin to wane.
    73
    KarapuZ

    ReplyDelete
    Replies
    1. Dear KarapuZ, Cpacibo, Thank you very much for the received info, and noted that your antenna situation is not the best possible option to receive 29.4 MHz signals. Please let me know if you have some hamradio "callsign" and if you have, please register to the "DX-SPOT" of BATC at: https://dxspot.batc.org.uk/ this would give me the possibility to trace the exact direction and distance between our 2 stations. For your info: next Sunday 7/12 from about 9h30 Brussels time and if the conditions permit I will be doing more tests with my friend Stavros SV1EBS on +- 29.4MHz. After these test I could turn my antenna in your direction, we can communicate via the chatmode on the DX-SPOT or on zello ATV channel. I speak English, French, Dutch, Italian, German and some Spanisch but sorry "pa ruski nipanimaiu"
      73's Frans ON4VVV

      Delete
    2. Dear KarapuZ, it is really surprising that you could receive and demodulate my D-ATV signals even with your antenna facing in the wrong direction and not ideally suited for 29MHz. I will be doing some more testing next sunday from 9h30 Brussels time. Please register to the DX-SPOT from the BATC here: https://dxspot.batc.org.uk/ and fill in or a Callsign or a name like KarapuZ so that i can find the exact distance and direction to you. after finishing my test with my Friend Stavros SV1EBS in Greece I will turn my antennas in your direction to make the same test with you. for the communication we can use the chat function of the DX-SPOT I can talk and understand English, French, Dutch, Italian, German and a little Spanish but sorry "Pa Ruski Nipanimaiu". very 73's Frans ON4VVV

      Delete
  4. Dear Frans, this Sunday I'll still be recording 29 +-3 MHz as IQ data. Thank you very much for announcing your DVB-S2 tests!

    Unfortunately, I don't have an amateur radio callsign; perhaps I'll get one when I retire. However, I have extensive experience as an HF radio observer. I'm interested in radio signals and their technical analysis, including analyzing radio transmission protocols, demodulation, and decoding.

    My busy schedule (work and family) forces me to pursue my hobby mainly in the evenings, and often late at night. I'm very grateful for your offer. Perhaps the best option would be, after completing the tests with SV1EBS, to point your antenna at my loc. KN95bg and, if you don't mind, conduct short transmissions (a few minutes each) in 33, 66, 125, and 250 kbps modes. If conditions permit, we'll see the difference in signal levels, the percentage of LDPC corrections, etc. My demodulators can extract the transport bitstream from DVB-S2 up to 8PSK, 16, and 32 APSK modes at any speed.
    Recording will automatically start at 08:00 UTC and continue until 16:00 UTC.

    Dear Frans, I appreciate your feedback and suggestions! Unfortunately, some circumstances require adjustments. I wish you successful tests.

    P.S.:
    My colleagues are wondering why DVB-S2 was chosen for HF. Wouldn't DVB-T2 (OFDM) be preferable?

    73
    KarapuZ

    ReplyDelete
    Replies
    1. Dear KarapuZ,
      thank you for the respons. Can you also let me know the signal strength when I am transmitting in the direction of my friend SV1EBS and let me know the difference when afterwards I will be in your direction. This will inform me about the horizontal radiation diagram of my 4el antennabeam. Of course when I go from 33 to 66 ks/s, there should be an average difference of -3dB each time the SR is doubled from the previous.
      So far it looks like that the conditions continue to be good enough for an ongoing test tomorrow morning..
      Question: can you demodulate 8PSK, 16 and 32APSK with SDR console and SDR television??
      Re DVB-S2 and DVB-T2: indeed most probably DVB-T is better to overcome multipath etc but the amplifiers must be much more linear resulting in a power level devided by 3 against DVB-S2 and there is also the difficulty to generate very narrow DVB-T2 signals instead of DVB-S2. In any case it was my intention to do this tests sooner or later.
      Please register on the dx-spot and let me know the used name, I would like to show our connections on the BATC map.

      very 73's
      Frans ON4VVV

      Delete
  5. Dear Frans, I'm ready for tomorrow's tests.

    But, unfortunately, the "registration" button in response to your request on the resource
    https://dxspot.batc.org.uk/ is inactive for me... The resource is likely screening my IP as "unwanted," and perhaps this can be circumvented using a VPN on my end, but my civic position prevents this.

    If all goes well, signal levels can be calculated from my IQ data records.

    Best wishes!

    The equipment is warming up.
    73
    KarapuZ

    ReplyDelete
  6. P.S.
    Regarding your question, SDRConsole and SDRTelevision, as far as I know, are currently unable to demodulate and process 8PSK, 16, and 32APSK DVB-S2 modes, unfortunately.
    Perhaps Simon will add these modes later.
    73
    KarapuZ

    ReplyDelete
    Replies
    1. Dear KarapuZ,
      I am very sorry but I am unable to transmit today, I have sudden familial obligations blocking my sundaymorning.
      very best regards
      Frans

      Delete
  7. dear KarapuZ,

    I can create an account for you on the DX-SPOT if you want, I only need your Email address for that..
    vbr Frans

    ReplyDelete