I used to work at the VLA as an RF engineering intern. I learned a lot. There is a good technical answer in these comments already, in regards to reception.

But AO was also a transmitter - it could pump out millions of watts to illuminate asteroids, the moon, and other orbiting objects for mono static and bistatic radar measurements. For example, images such as these [0] are created by receiving the reflection of energy emitted from transmitters like AO and Goldstone (I didn’t find an exact image of an AO-VLA measurement but they’re out there).

The AO and VLA had a unique relationship, in that one could precisely measure and image irregularities of any particular VLA dish panel down to a few tenths of a millimeter using bistatic radar of the moon. It’s somewhere in the eVLA library but my google fu is failing me (also google really sucks now).

They also had a few events for ham radio where AO lit up the moon and hams across the world could hear its reflection with basic equipment. [1]

[0] https://m-cacm.acm.org/careers/182810-high-def-radar-images-...

[1] https://youtu.be/SUr1z5XeOE0