I reckon to do 3G and achieve the level of isolation required should you end up using adjacent RF channels, you'd need some rather more serious filters / higher-spec (read: tighter) amplifiers in the RF path as well. Pricey.

Sure, you could do this. But to have 3G standby for 2 bands at once the end product would be a LOT bigger than current devices.

Jump in here Dean on the subject of divergent devices, but I'm pretty sure the user case here is pretty niche. By the look of it, Normobs/business Normobs (Bormobs?) are actually happy with separate devices, thanks very much.

/m

I want one or more numbers which can be directed to any of my phones at any time (or do more clever things like ring several) and for outgoing calls / SMS to present that number. I want the handsets to be on any network I like, for which I'd pay a connection subscription, but for calling from any handset to be billed from a single provider that covers the lot and to whom I either pay according to a tariff or buy a bundle. I want to break the one number / one handset model and do it in a more elegant way than the current solutions which get close-ish.

It MUST be the operators refusing to stock dual sim handsets. That must be the reason.