If like myself you live in a country with 220-240V AC mains supply, and use the US (and only) version of the SmartThings Hub, your Z-wave network operates at 908,4MHz.
The Aeon Labs DSD37/US Range Extender operates at 908,4MHz, comes with a US plug but is specified only for 120VAC/60Hz operation; it also comes in a EU flavor [868,4MHz, 240VAC/50Hz], whose frequency is unfortunately incompatible with the SmartThings hub.
I just checked the insides of both a DSD37/US [908,4MHz, 120VAC/60Hz] and a DSD37/EU [868,4MHz, 240VAC/50Hz], and it happens that those 2 versions use exactly the same internal power supply.
The good news is thus that you can use on 240VAC the Aeon Labs DSD37/US Range Extender with a SmartThings hub, using a simple US->EU plug adapter, without the need of a more bulky and expensive 240V->120V converter.
Beware however that Aeon Labs may change at any time the internals of its DSD37/US, so what is true today may not be true tomorrow : YMMV, try at your own risk…