You have more patience than I do with the ongoing answers to the question you did not ask. (Sheesh guys, he has said several times he is aware !

The NanoVNA is not able to make accurate, repeatable level measurements on the S21 port for any signals other than CW. The reason for this is all power from the signal being measured must fit inside one of the "bins" in order for the value to be correct.

FM broadcast signals in the US occupy 150 kHz. If, during the measurement, all 150 kHz of the signal just happen to fall inside one of the "bins" then that particular power measurement can be accurate. This is why CW can be measured and FM/AM/TV cannot.

When the signal spreads beyond one bin then you would see multiple signals with varying amplitudes that are different with each VNA sweep.

On the other hand, level measurements of CW signals are stable, and as accurate as your calibration allows. Measurements of CW signals down to about -80 dBm are accurate and repeatable.

Warren Allgyer - WA8TOD