- This standard defines interoperable characteristics of an SHF satellite communications modem. A modem compatible with this STANAG will be used to provide communication links through transparent satellite transponders. The purpose of this standard is to ensure modem to modem interoperability between NATO forces utilising SHF transponding satellite systems. It is intended that this standard be applicable to all geosynchronous SHF satellite systems. This standard defines the interoperable characteristics of an SHF satcom modem for low datarate services defined as Class A in STANAG 4484.