Why Do You Need So Many Radio Telescopes?
Question: Why do you need so many radio telescopes? Do they all receive exactly the same frequency? How are the signals integrated into something meaningful? — Ray
Answer: You basically hit on a part of the answer in your second sentence. Different radio telescopes are designed to make measurements at different frequencies. For example, we build very high-performance antennas to make measurements at high frequencies. At lower frequencies, we can relax these performance requirements and make them larger. Another reason for building more than one radio telescope is that we have basically two different techniques to make radio astronomical measurements. One is to just make measurements with a single antenna (like the Green Bank Telescope), and the second is to electronically connect many antennas into an array of radio telescopes (like the Very Large Array) in order to increase the amount of collecting area the spatial resolution on the sky of the measurements we make. Finally, since one cannot see the entire visible sky from one place on Earth we need to place telescopes at different places on Earth to be able to observe in all directions.
Jeff Mangum