[amsat-bb] Re: S band interference solution

John Champa k8ocl at hotmail.com
Thu Oct 5 13:34:39 PDT 2006


You are NEVER going to hear your neighbor's WiFi @ 10 miles!  Come on, Bob!

I have experienced this near / far phenomenon of which you write many times
It is something in the RF environment with which we need to learn to deal.
I work in a location where I normally monitor 40 -60 WiFi devices at the 
time, yet I manage to get a signal through such nasty terrain.  A hand-full 
of neighbors
wouldn't make me completely re-design an OSCAR and drop an entire 

You must be one of those pessimist we were writing about earlier.
Put the math aside and go out to your front yard and meet those fine WiFi 
folks! (HI)

Vy 73,
John Champa - K8OCL
Former Executive VP - AMSAT

>From: "Robert Bruninga" <bruninga at usna.edu>
>Reply-To: bruninga at usna.edu
>To: <AMSAT-BB at amsat.org>
>Subject: [amsat-bb] Re: S band interference solution
>Date: Thu, 5 Oct 2006 15:28:09 -0400
> > > These are 100 mW devices...maximum!  That means they have
> > > to be relatively close to your QTH for you to hear them.
>Two big words there.  "Relateively" and "close"...
>The laws of physics trumps all opinions...
>All of these give the SAME power at your antenna:
>  - A 100mW device at 1 mile
>  - A 10 W  device at 10 miles
>  - a 1000W  device at 100 miles.
>Or this one:
>  - A 100 mW device at 10 miles
>  - A 10 Watt device at 100 miles
>  - A 1000W device at 1000 miles LEO
>  - A 400 Kw device at 20,000 miles GEO orbit
>Now our birds do not have 400 Kw to downlink at S-band to
>Your neighbor's WIFI at 10 miles away.
>Even if you throw away 30 dB of antenna gain  (the neighbor will
>not be in you main lobe, this then makes the 400W Satellite
>coming in your MAIN beam no stronger than a neighbor at 10 miles
>away with a 100mw device coming in the back of your dish.
>Yes, it is only 100 mW, but when it is 20,000 times closer, it
>is 400,000,000 times stronger.
>De WB4APR, Bob
>Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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