Re: Arecibo on 432 MHz Moon Bounce (some calculations)
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.
I guess because it's impossible to build an isotropic radiator and therefore just as impossible to measure it. Why would I believe, or want to use, something I can neither have, use or measure?
An isotropic antenna doesn't exist.
On 22-Apr-10 10:20, Stephen Melachrinos wrote:
In fact, the amateur community is the only place where there is a fascination with the dipole reference.
The mathematical model is well proven. The difference between a isotropic and a dipole antenna is 2.1 dB. The practical accuracy of field strength measurements on a antenna range is +/- 3dB, making this whole discussion theoretical. (Just In The Interest Of Science) or JITIOS! Art, KC6UQH -----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Nigel Gunn G8IFF/W8IFF Sent: Thursday, April 22, 2010 6:15 AM To: w3hf@arrl.net Cc: amsat-bb@amsat.org; Stephen Melachrinos Subject: [amsat-bb] Re: Arecibo on 432 MHz Moon Bounce (some calculations)
I guess because it's impossible to build an isotropic radiator and therefore just as impossible to measure it. Why would I believe, or want to use, something I can neither have, use or measure?
An isotropic antenna doesn't exist.
On 22-Apr-10 10:20, Stephen Melachrinos wrote:
In fact, the amateur community is the only place where there is a
fascination with the dipole reference.
participants (3)
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Art McBride -
Nigel Gunn G8IFF/W8IFF -
Stephen Melachrinos