Ah, but this focuses on my question: Why is ERP referenced to a dipole? Why did someone assume that Arecibo's stated gain of 60 dB was dBd and not dBi? I've never seen the gain of a dish antenna used in satellite work quoted in dBd. All of the references for calculating gain are based on the isotropic reference. And all of the usages I have seen (in professional satellite work) use ERP and EiRP interchangeably, and the i in EiRP is used to explicitly state "referenced to isotropic."
In fact, the amateur community is the only place where there is a fascination with the dipole reference.
The dBd specs are useless for any real calculation purposes. Satcom engineering is much simpler if everyone quotes isotropic, and all commercial/government/military satellite link budgets are based on isotropic references.
Steve Melachrinos W3HF (Professional) Satcom Engineer since 1979
"ERP is about 243 MW" and that comes from the conversion from dBi to dBd.