FW: info on digital ATV modules

[Paul L Rinaldo]

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Gang,

You'll remember Uwe Kraus who visited us last year. Here's an update of his
digital ATV project.

Paul

>-----Original Message-----
>From: Klaus Kramer [mailto:DL4KCK@t-online.de]
>Sent: Sunday, March 24, 2002 6:55 PM
>To: Gene Harlan; k8ocl@arrl.net; Chairman@batc.org.uk; graham Shirville;
>Ian Pawson; Marc Chamley; Michel Vonlanthen; Mijo Kovacevic; REPEATER;
>Michael Kastelic
>Subject: info on digital ATV modules
>
>
>Hello,
>
>for your kindly observation here some exclusive news, there are two
>different groups working on Digital ATV in Germany: one for QPSK 
>modulation on GHz bands only (d-atv) and the older one for a universal
>solution from 70 cm (GMSK only) to 24 GHz with four modulation variants
>now (datv-agaf.de), see attachment.
>
>
>vy 73 Klaus, DL4KCK
>
>
>
>
>Attachment Converted: "c:\eudora\attach\Digital_ ATV_e.txt"
>
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Digital Amateur Television (DATV) Field-Tests in Germany Extended

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 re-transmitted. 

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

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

PS: pictures and block diagrammes available at www.datv-agaf.de

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