In Detroit, most Canadian contract phones from neighboring Windsor include Metro Detroit in their coverage area. You can also get a true Rogers signal as far back as Comerica Park which is probably two miles in. My personal feeling is that they should allow this cross-over signal, but too many people call and try to reverse charges because they are too clueless to see what carrier they are on.

In southern Helsinki, Finland, phone can sometimes switch to estonian carrier.. Distance is more than 70 kilometres. Signals can pass over the sea quite well...

Doesn't GSM have a 35-km limit for the signal?

Normal GSM has about 35km limit, but some operators are using coastal/ rural areas etc. technology called "extended cell-feature", which can make 2-3 times longer range..

Btw. In Australia they have launched 200km range 3G.. Australia Gets 200km Wide 3G Cell Sites

on holiday in greece we picked up 2G and 3G signals from Malta - which is nearly 1000km away on some days! -- and on one day 2G from Lybia, 1300km distance, Quite impressive.
Of course you are not able to register to the network as the runtime of the signals it too long but you can see these operators on the op search.

Chris

If it's 1000km away only on some days, where is it the rest of the time? ;) I always knew Malta was just a floating ship!

I think the effect that you describe is due to 'tropospheric ducting' which typically occurs over large bodies of water. I guess it is the same effect that allows you to pick up FM radio signals from across the sea when there are just the right atmospheric conditions.

yeah, my sentence was a bit messed up. Of course Malta is always 1000km away - but you can not always pick the signals. Only if there is a duct as you already described.