[amsat-bb] Re: Arecibo on 432 MHz Moon Bounce (some calculations)

Stephen Melachrinos melachri at verizon.net
Thu Apr 22 03:20:06 PDT 2010

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
(Professional) Satcom Engineer since 1979

> "ERP is about 243 MW" and
> that comes from the conversion from dBi to dBd. 

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