Radar and satellite systems still use traveling-wave tubes in the RF signal chain. The reference to tubes could also be the radar displays, which were traditio

Radar and satellite systems still use traveling-wave tubes in the RF signal chain. The reference to tubes could also be the radar displays, which were traditionally vector CRTs. https://en.wikipedia.org/wiki/Traveling-wave_tube https://en.wikipedia.org/wiki/Traveling-wave_tube