www.hb9afo.ch
DATV- Digital Amateur TeleVision

By Michel Vonlanthen HB9AFO
 

These articles were mainly done when i was the the ATNA (Amateur TV of North America) representative in Europe. Badly, this association has now resumed because lack of interest and cooperation. But in french language, I have continued this serie named

Digital ATV ? This is not so complicated !

You will find in it a lot of interesting informations about DATV. If the interest is great, I can one time translate it. Intertime, you will find the DATV theory here. You will also see infos and links about ATV/DATV on my web site:

www.hb9afo.ch
 

 

2009 january    DATV Transmitters

That we can obtain or build actually.
 

  • AGAF (2003)
    430 MHz, 2 prints 100 x 160mm.
    Settings only by jumpers
     

  • SR-SYSTEMS (1st version 2004)
    2 basic prints and the HF section can be 430 ou 1200-2400 MHz. Settings by PC.
     

  • F4DAY (2004)
    Entirely home-made system and only with currents components.
    Beautiful to learn how it works!
     

  • F1JBB (2007)
    Sold only built and tested.
    Actually, we have no news of this development.
     

  • SR-SYSTEMS (2nd version, 2007)
    Compact: only 2 cards. Front panel with LCD and switches  (no need for a PC)
     

  • AGAF (4th generation 2007-2008)
    All will be only on one board. No date of delivery today.


2002 july    Rudolf Horkheimer Award 2002 for DATV Team

Prof.Dr.-Ing. Uwe E. Kraus, DJ8DW, received the DARC Rudolf Horkheimer award 2002 on behalf of the DATV working group at Bergische University Wuppertal. DARC board member Dr. Walter Schlink, DL3OAP, handed over the award to Uwe Kraus, DJ8DW, and Hans-Juergen Schmitz, DJ8VR, during the opening event of HAM RADIO 2002 fair end of June in Friedrichshafen, Germany. In his speech DL3OAP appreciated the outstanding development by the DATV group and stressed the fact that Uwe Kraus devoted himself to the UHF bands and the amateur television technology soon after having received his licence in 1962.
Latest DATV lecture sheets from DJ8DW with block diagrams and pictures of the new 3rd generation MCBs, results from field tests on 70 and 23 cm and future developments are ready for download at www.datv-agaf.de/.

Klaus, DL4KCK, AGAF


2002 march    DATV field-tests in Germany

Since November 2001 the DATV transmitter designed by a group around DJ8DW at Bergische University Wuppertal is working properly on 23 cm (1255 MHz) in Cologne at the ATV-repeater site DB0KO. The transmitter, which may be programmed to various digital modulation schemes and data rates, at this site is programmed to QPSK and according to the DVB-S standard. Thus a reception is possible by a cheap digital satellite TV set-top box along with a preamp if required. The repeater FM ATV input signal is demodulated to baseband PAL, converted to MPEG II (5 MBit/s) and digitally retransmitted. 

The repeater output can be switched between FM ATV and DATV by DTMF remote control thus allowing a fair comparison. In a distance of about 50 km the FM signal (repeater output power 20 W, 18 MHz bandwidth) resulted in a rather noisy picture whereas DATV (repeater output power 10 W, 6 MHz bandwidth, same 10dB omnidirectional antenna) showed a perfect picture. Although the set-top box has no echo equalizer there were only very few problems with multipaths reception most likely due to the fact that the repeater is installed on top of a building 150 m above ground and that highly directional receiving antennas are used.

In the meantime the tests are extended in the Wuppertal area to 70 cm (center frequency: 434 MHz, bandwidth: 2 MHz, data rate: 2 MBit/s, transmitter power: some mW through 80 W). Omnidirectional as well as highly directional antennas are used. The tests are covering field strength measurements at various places in rural and urban areas, check the multipath situations as well as possible problems which might be caused by ISM interference. In addition DATV-DX tests are performed.


DATV-Buildingblocks in preparation


Encodeur MPEG-2

Emetteur DATV 434 MHz

The MPEG II encoder board and the DATV transmitter board are currently prepared for a small-scale production series organized by AGAF. These boards ready built and tested will be available in some months time for licensed Radio Amateurs and for amateur applications only, the price is calculated on a no profit no loss base. Ordering information is available from AGAF by fax (+49 231 486 989) or via Internet at www.datv-agaf.de (commercial applications may be possible under a special contract with the Wuppertal University). 


Specifications of the boards

General: Both boards, MPEG II encoder and DATV transmitter, have standard signal input/output interfaces. They may be used together for DATV but also separately for other applications. The various digital modulation schemes and data rates are generated on the transmitter board with 10 mW on 434 MHz and are selectable by jumpers or switches. Modulation schemes generating 2 MHz rf-bandwidth may be transmitted on 70 cm, all others with a higher rf-bandwidth are heterodyned to the GHz bands.

1: MPEG II Encoder (Fujitsu encoder IC)

  • Input: analog PAL/NTSC, Y/C, stereo sound

  • Output: 2 x standard MPEG II bit parallel, data rate selectable from 2 Mbit/s - 10 Mbit/s

2. DATV Transmitter

  • Input: live MPEG II bit parallel, hard disk recorder, on-board plug-in memory card containing

  • short moving video scenes which may be transmitted cyclically for long time tests or station identification

  • Output: 434 MHz rf-DATV-signal, 10 mW, 50 Ohm SMA, 36 MHz or 44 MHz if-DATV-signal

  • Digital modulation schemes available: QPSK (DVB-S), GMSK, QAM, 8-VSB (ATSC)

  • Power: Single 12 Volt (10 V - 14 V), ca. 600 mA each board

  • Size: 100 mm x 160 mm Euro, 4 layers

Uwe, DJ8DW
Translation Klaus, DL4KCK


2001 june    Digital-ATV at Ham Radio 2001

The digital Amateur Television test provided by a group around DJ8DW from Wuppertal university at the HAM RADIO 2001 fair in Friedrichshafen, Germany, was built up over a 9 km distance from the "Elektronikschule Tettnang" building to hall 6. On  434 MHz plus/minus 1 MHz 80 watt power output were used in GMSK modulation and a fourfold 11-el. yagi group at each location.

On Friday morning the video and sound transmission in MPEG2 quality was successful at times, but strong inband short-time
carriers interrupted it more and more. So an originally planned long path test over 26 km from Austria was cancelled.

Several TV monitors at the combined stand of DARC public relations and AGAF e.V. were showing all three days long, how well an
undisturbed 3. generation digital-ATV link can work. On 1255 MHz plus/minus 3 MHz 10 mWatt in QPSK modulation with FEC (forward error correction) provided excellent video and sound quality, received by a cheap digital satellite TV settop-box in MPEG2.
After intentionally interrupting the path an error message from the settop-box menue appeared on a black TV screen, but after  realignment the live picture was back with some delay.

Uwe Kraus, DJ8DW, will soon present a detailed description of 3. generation DATV which is designed to enable experienced
TV amateurs to use the new single chip MPEG2 coders and decoders from Fujitsu and a universal modulator for GMSK, QPSK or 8VSB.

Klaus, DL4KCK
AGAF e.V.