[opendtv] Create DVB-T RF with your VGA card

  • From: "John Shutt" <shuttj@xxxxxxxxx>
  • To: "OpenDTV" <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 21 Jun 2005 12:57:30 -0400

Any takers on the 8-VSB hack?



Don Lung's RF Report

Use Your PC VGA Card to Generate DVB-T RF

Although I haven't been able to verify this actually works, I thought 
readers would be interested in a Web site describing how to use a PC running 
Linux and a current generation video card to create a modulator capable of 
generating a VHF DVB-T signal. At present, the system does have some 
limitations. It can only transmit still images and the DVB-T signal 
containing the images has to be computed separately before it is sent to the 
VGA adapter.

If you are interested in trying out this modulator, you will need a PC with 
a recent VGA card able to display resolutions up to 4096x2048 using 8 bits 
per pixel with a pixel clock of exactly 76.5 MHz. The ATI Radeon 9200SE 
cards are reported to work, according to the Web site. The video card's red 
digital to analog converter output (signal pin 1 and ground pin 6 on a 
standard 15 pin VGA connector) is used as the RF output. The output power is 
very low so you will likely need to make a cable to feed the RF to the TV 

The DVB-T modulator also requires use of Linux and the X Window system on 
the PC. The X Window server allows custom configuration of the video card's 
output signal. Using precompiled files from the Web site, you can generate a 
valid 16-QAM DVB-T COFDM-2K output signal receivable on channel 5 (178.75 
MHz) with two channels, each with a still picture.

For details on this interesting experiment, files, and additional links, see 
Use your VGA Card to Transmit DVB-T signals! A Low Cost Analog and Digital 
TV (DVB-T) Modulator. <http://fabrice.bellard.free.fr/dvbt/>

Who will be the first to use similar techniques to generate an 8-VSB signal 
on a U.S. TV channel using a video card? As the 8-VSB signal is less complex 
than the COFDM signal, it seems this wouldn't be too difficult! If you 
succeed, please let me know! As we make the transition to digital TV, there 
will be a need for low-cost test equipment and ideas like this that 
challenge engineers to learn more about DTV transmission. 

You can UNSUBSCRIBE from the OpenDTV list in two ways:

- Using the UNSUBSCRIBE command in your user configuration settings at 

- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word 
unsubscribe in the subject line.

Other related posts: