The VLBA antenna at Fort Davis, TX, is an example of a typical VLBA antenna. The dish is 25 meter (82 feet) in diameter, and when pointing straight up, the antenna is as high as a ten story building.
The antenna works just like a Cassegrain reflecting optical telescope. The signal is reflected by the dish to the subreflector; the position of the subreflector determines which receiver will be used. In an optical telescope, the mirror (dish) reflects light to the secondary mirror (subreflector) and then into the eyepiece (receiver).
The next stop on the signal path will go into more detail about the elements of the antenna.