The Sun is an extraordinary workbench to accurately calculate several fundamental stellar parameters.
Among these parameters, the solar radius have been the subject of increasingly accurate measurements and investigations.
To date several models were constructed in order to reproduce quantitatively not only the solar disk, but also the solar atmosphere from radio observations.
Despite the importance of having an accurate measurement of the solar radius and a deep knowledge of the corona, these subjects are still a matter of debate in the literature.

In this talk I'll present the first results about the measure of the solar radius and the evidence of the coronal physical emission in the 18-26 GHz band (up to 100 GHz in perspective) with the large single-dish INAF radio telescopes, throughout 5 years, from 2018 to early 2023.
The coverage of the entire solar disk, the low noise, the accurate absolute calibration, and the great sensitivity of INAF radio telescopes make these data crucial to accurately observe the solar corona.
Using about 300 radio solar maps obtained in the context of the SunDish project, devoted to the radio imaging and monitoring of the solar atmosphere through the INAF radio telescopes (Medicina 32-m and SRT 64-m), I'll describe our methods to calculate the solar radius and to prove the physical origin of the coronal emission; finally, I'll discuss and comparate our results with respect to the literature.