they use 230-ft in diameter dishes on earth to send 20kw signals to the craft.
"Successfully sending a DSN signal into Voyager-2's receiver is like throwing a baseball across thousands of miles of ocean into a porthole of a moving cruise ship."
so imagine how much more difficult it is to reach Voyager-1, 1.6 billion miles fruther away.
supposedly, Voyager-1 won't run out of electrical power until 2020