I have received my self install Sagecom Router/Modem. I has a sim card fitted so anticipate the 4G modem is installed. It came without an antenna. I know from in depth past experience this is a requirement for the modem to operate efficiently.
There is no external antenna that comes with the Modem Kit, it has an internal antenna, if you need an antenna for coverage, there is connectors on the back hidden under the flap, but you will be required to purchase your own. Before purchasing, unplug your NBN to make it go to backup and see if it works without, if you have mobile coverage on a handheld there should be no need for external antennas.