Yes, ANTENNAS is a Scrabble word!

Letter values in Scrabble US: A 1, N 1, T 1, E 1, N 1, N 1, A 1, S 1.

Is it a valid word?

ANTENNAS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

an electrical device that sends or receives radio or television signals
sensitivity similar to that of a receptor organ
one of a pair of mobile appendages on the head of e.g. insects and crustaceans; typically sensitive to touch and taste

Also: transmitting aerial.