why in the USA GSM networks work on 850\1900 MHz unlike European 900\1800MHz?

Some of the reasons are technical. i.e. spare slots.

Some of them are however political. With GSM, there is a bit of a 'not invented here' attitude in the US. Chosing different frequencies to the rest of the world sends a subtle message like: 'CDMA is best. Of course we will allow GSM networks in the US, but we'll make it more difficult for you by choosing a different frequency' Since 1983 when the mobile communicatipons start to patronize and used around europe and united states those are the set bandwith in order to avoid interference and setting allocation for certain mobile comunication Each country sets it's own rules and regulations regarding radio frequency use. Sometimes this was done by committee. Sometimes these rules are built around existing uses. If a frequency or band of frequencies was all ready in use, they simply put the proposed services into unused areas.

When countries are next to each other, like the US and Canada, then treaties are adopted by the affected countries. Look at all the countries in Europe. They must have had a lot of negotiations to find common frequencies.

I guess the best example might be cars. Some countries drive on the right, some on the left. Both work just fine.

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