[Ennio]

I ordered a Revo, and I just noticed that the OPLink modem is running at 433Mhz, is this ok to use in the US or does it need to be 900Mhz?

[hwh]

Using a 433 MHz oplink in the US probably requires an amateur radio license.   That said, while I have a license most users probably don't and either don't know or don't care.

Currently all the oplinks being made commercially are 433 MHz, to get a 915 MHz one you have to buy a 433 and replace the 433 MHz RFM22b with a 915 MHz one.

We're hoping the Chinese will start making 915 MHz (and 868 MHz) ones.  Support for them is in the next release of LibrePilot.   It probably needs users to contact sellers and ask for the 915 ones.  If they think there's a demand they'll probably make them.

[startrek66]

The frequency band 433 MHz is also used by services which do not require amateur radio license, for example the rtx lpd. Then a lot depends on the band plan of each state.