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Potentially, optical (laser) transmitters have a lot more bandwidth, but need very fine aiming control. At those distances, a high-gain antenna would have to be too large to be feasible, even with an extensive upgrade of ground-based receivers.

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In the book "Voyager : seeking newer worlds in the third great age of discovery" they said that as the crafts got further out they had to use large radio antenna's in Spain, Hawaii, and Australia to lock onto the signal, creating an Earth-scale virtual antenna.

Truly amazing stuff.

These are part of NASA's Deep Space Network, used to communicate with the fleet of interplanetary spacecraft (as well as plenty of satellites and the ISS). The you mentioned the three largest ones, each with a 70 meter dish.

And here's the pic:

http://deepspace.jpl.nasa.gov/dsn/images/picture_70_bw_lg.jp...

Now that we're talking about big telescopes I can mention LOFAR: http://en.wikipedia.org/wiki/LOFAR

It's interesting in that it consists of 15.000 small antennas and they are using computers to combine the signals which effectively gives you a 1 square kilometer "dish".

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