Assertion: spectrum's frequency | /r/ObjectUse | used for radio communication
Facets:
Source sentences:
text: The lowest frequencies used for radio communication are limited by the increasing size of transmitting antennas required.
text: The lowest frequencies that have been used for radio communication are around 80 Hz, in ELF submarine communications systems built by a few nations' navies to communicate with their submerged submarines hundreds of meters underwater.