A BBC crowd-sourcing survey into the state of mobile Britain suggests that 3G has some way to go before it offers comprehensive coverage across the UK.
Despite operator claims of 90% or more 3G coverage, there are still many notspots, including in major towns and cities, according to the map.
Those testers able to receive a data connection only got a 3G signal 75% of the time.
For nearly a quarter of the time they had to rely on older 2G technology.
2G is typically around ten times slower than 3G "mobile broadband".
Mobile coverage has become a huge issue as people rely increasingly on their smartphones to surf the web and send email as well as making phone calls.
Last month the BBC invited people to download an app that would collate the 3G coverage their Android handsets were getting.
The experiment aimed to offer a snapshot of coverage.Industry first
44,600 volunteers took part, providing testing firm Epitiro with some 1.7 million hours worth of data from around the UK.
"The BBC has undertaken a crowd-sourcing survey that is well beyond any scale seen by the mobile industry in this country or any other," said Gavin John, chief executive of Epitiro. Continued