How 3G Frequency Compatibility Works / Why Your Unlocked Phone Doesn’t Get 3G

Ok, so I’ve realized that a lot of people see all the cool phones over in Europe, buy them here in the States for use on T-Mobile or AT&T (myself included) and all is fine and dandy but then they wonder why they don’t have 3G when on the box of the phone it clearly states 3G enabled…

I wanted to explain why this happens.

So basically 3G is dependent on two things; what frequencies the phone has built in that it can see and what frequency the phone company you want to use is projecting their 3G network on.

Let’s start with the latter factor. Here in the US, we have two GSM carriers that both have 3G; AT&T and T-Mobile.

AT&T projects their 3G network on 1900mhz (and recently started projecting on 850mhz as well).
T-Mobile projects their 3G network on 1700mhz (and we believe owns 2100 but isn’t using it yet, see 3G Revelation post for more details on that).
Most European phone companies (where most unlocked phones are made for) use 900mhz or 2100mhz to project their 3G networks.

Since most unlocked phones are made for European use, they have 2100/900mhz receivers built in. So if you are using that phone on a network that uses either 2100mhz or 900mhz, you’re phone will be able to see the frequency and get 3G data.

On the other hand, when you bring that phone over here to the States and try to use it on T-Mobile or AT&T’s 850/1700/1900mhz 3G networks the phone simply cannot see these frequencies and can only get up to EDGE connectivity. (The phone works fine, but you will not get 3G data speeds).

So bottom line, when you buy an unlocked phone for use here in the US, make sure that it says in the specs for 3G (sometimes called HSDPA or HSPA) that at least one of the frequencies match your carrier’s 3G frequencies if you want to use 3G. Otherwise, get one with Wifi and hope you can find some free hotspots around…

Now, when you buy a phone from your specific carrier here in the US (as most Americans do) they had that phone specially made for them by the manufacturer (and branded with their logos etc.) and had the manufacturer put their 3G frequencies in it (sometimes they leave 2100mhz as well for those people who want to goto Europe with their phone).

Now, this brings me to question something though…
Why wouldn’t a manufacturer, who knows that a lot of people won’t buy a phone if it doesn’t get 3G where they live, just put ALL the 3G frequencies in everyphone they make (called PentaBand 3G for the 5 frequencies; 850/900/1700/1900/2100mhz)? It can’t cost that much more to put the other 2 or 3 antennas into the phone and it would open their phone market up to anyone in the world (and also stop them from having to make differing versions of the phones for just that reason, i.e one for North America, one for Europe, and one for Asia).

Anyone have any better idea than I as to why the manufacturers won’t do this?

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