Cheap prepaid Internet for short stay in Germany? [merged]

[inquisitor]

Originally Posted by siskiou

There were many not covered areas along the train route from Duesseldorf toward the coast (Norddeich), but it *is* a very thinly populated area along the way.

Coverage inside long-distance trains is an issue, since modern IC (InterCity) and ICE (InterCityExpress) wagons have metal-coated windows and a steel frame, which severly attenuates radio signals (up to 30db in a ICE). Allthough a lot of waggons have so called intrain-repeaters installed, older ones do not work for O2 and eplus, as these two operators use EGSM900 and GSM1800 but older repeaters do only amplify the PGSM900 band and eplus' portion of the GSM1800 band. 3G is not amplified by those repeaters at all. According to press releases german rail operator Deutsche Bahn is about to swap those old GSM repeaters, but if you're in a waggon without repeater or with an old repeater, you'll experience bad network coverage.
Upon request seats can be reserved in waggons with repeaters, which carry this symbol:

For more details in German see Intrain-Repeater ? Wikipedia