It's generally not recommended to put a radio or any electronic device directly on top of a microwave while it's in use. Microwaves emit electromagnetic radiation during operation, and this radiation can interfere with the functioning of nearby electronic devices, including radios.
The electromagnetic interference (EMI) from a microwave can cause static, distortion, or disruptions in the radio's signal, leading to poor reception or even temporary damage to the radio's components.
To avoid potential interference, it's best to keep electronic devices, including radios, at a safe distance from the microwave while it's in operation. A distance of a few feet should be sufficient to reduce the risk of interference. Once the microwave is done cooking, it should be safe to place the radio back on top if you wish.
Additionally, it's essential to follow the manufacturer's instructions and safety guidelines for both the microwave and the electronic devices you own to ensure proper functioning and prevent any accidents or damage.