ALMA is the main example of radio-telescope located in Chile. And, what an example! the most powerful radio-telescope in the world working at millimetre and sub-millimetre frequencies. Although there are bigger single dish radio-telescopes in other places, ALMA outperforms them in general. A bigger radio-telescope has a higher sensitivity because it collects more "light" (radio waves) but its field of view is very limited. A telescope like ALMA, composed of smaller dishes, can survey a bigger area of the sky than a single dish telescope. A good resolution is achieved using interferometry and the sensitivity problem is compensated by the use of many dishes.
As pointed out in other answers there are also other interesting radio-telescopes in Chile like, for example, APEX.
Why there are mainly millimetre and sub-millimetre radio-telescopes in Chile? Because mm and submm wavelengths are highly absorbed by the water in the atmosphere. To get rid of this problem you have to go to very high altitudes with very low content of water vapour. This make the high plains of Chile an exceptional place to build this kind of radio-telescopes.
Why there are not many mid and low-frequency radio telescopes in Chile? I can only guess, but these are some reasons that I can think about:
- Mid and low-frequency radio-telescopes do not require exceptional atmospheric conditions. In most cases it is possible to observe through the clouds. There is no point in locating these telescopes in a remote place in Chile when you can do that closer to your place for a lower price. I think this is the main reason.
- The astronomical community in Chile has a strong expertise in other wavelengths like optical, infra-red or mm and submm as mentioned. There is so much exceptional science to do in those areas that there was no need to push or focus in low and mid radio frequencies (at least not as much as to build their own radio-telescopes).
- Many current radio-telescopes are improvements made on old ones like the VLA. You do not need to build new dishes but focus in improving the receivers, the data processing, etc.
- Future radio-telescopes like SKA will extend over a vast amount of area. They need antennas located at very big distances from West to East which made Chile alone an unsuitable option.