I was travelling to uni for a 7.30am case conference last Wednesday (*groan*), which meant that I’d miss the last 15 minutes of the UEFA Champion’s League semi-final between Liverpool and Chelsea. I still wanted to catch the rest of the game, so decided I’d try to watch it on my MacBook using my USB digital TV tuner – an early-model Elgato EyeTV for DTT, employing the Terratec Cinergy T2 receiver with Elgato EyeTV 2 software.
In day-to-day use at home, I’ve found the EyeTV for DTT hooked up to either my iMac or MacBook to be an excellent setup for watching and recording digital TV broadcasts. This was the first time I’d tried to use the receiver on-the-move, and I was surprised to discover that the signal quality dropped to 0% (and consequent loss of video) at speeds above approximately 10 km/h, despite a signal strength in excess of 65%. When the vehicle was stationary, however, signal quality improved to 80–100% with restoration of video. This clearly implied an adverse Doppler effect on signal reception/decoding.
Australia uses the Digital Video Broadcasting—Terrestrial (DVB-T) standard for digital television broadcasts. A quick Google search confirmed my suspicions, with several papers describing the limitations of original DVB-T implementations with respect to mobile applications, owing to the high susceptibility to the Doppler effect (Tomasin et al., 2002a; Tomasin et al., 2002b).
This issue has apparently been addressed in newer multi-tuner implementations such as the Elgato EyeTV Diversity, which claims to maintain reception at speeds up to 160 km/h… Though I do wonder why designers of the original never considered that users might want to use their DVB-T receivers whilst travelling in cars/trains/etc. Liverpool drew the game. =/
Newer luxury cars with inbuilt TVs also have the same problem… although it’s disguised by the fact that whist driving, the TV is inoperable for ’safety purposes’.