[amsat-bb] Re: S-band Example
domenico.i8cvs at tin.it
Sat Sep 9 13:01:30 PDT 2006
----- Original Message -----
From: "Emily Clarke" <emily at clarke-design.com>
To: <bruninga at usna.edu>; <amsat-bb at amsat.org>
Sent: Saturday, September 09, 2006 7:56 PM
Subject: [amsat-bb] Re: S-band Example
> At 03:23 PM 9/8/2006, Robert Bruninga wrote:
> >Ok, now compare this signal to one from a 10 milliwatt 2.4 GHz
> >neighbor's phone about 150 feet away:
> > > PT is now 10 dBm
> > > GT is at worst 0 dB
> > > GR is say - 10 dB (35 dB worse than main lobe)
> > > LI is still about 3 dB
> I didn't see any loss attributable to the phone generally being in a
> building of some sort. I used to have one and it was useable to
> about 5 feet outside the house, and not useable much past there.
Bob computed a loss LS= -74 dB "building and concrete walls" included
for a distance of 150 feet away from the neighbor's phone.
In the example Bob uses the same antenna + receiver as used to receive the
satellite but the satellite antenna is now looking at the phone with an
angle so that the antenna pattern is 35 dB worse than main lobe and infact
GR= -10 dB
The gain GT of the antenna connected to the phone is assumed to be 0 dB
If you convert 150 feet in meters than you get 45.72 meters and using the
Bob formula the free space attenuation is exactly - 74 dB at 2.4 GHz
Adding the attenuation produced by wall and roof is very complicated
particularly if they are made using prestressed concrete with iron inside.
"But now the space loss, LS is not 40,000 km away, but only 150
feet away. And this computes to be a loss of only - 74 dB.
Adding it all up gives a power received of about - 77 dBm."
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