[amsat-bb] Re: Lightsquared Analogy

Bob Bruninga bruninga at usna.edu
Thu Mar 1 14:24:00 PST 2012

> In this case that would be wrong.  The headphone manufacturers 
> complained that good foam costs too much and were allowed 
> to get away with tissue paper and now everyone pays for 
> allowing lobbyists and lawyers run the FCC and ignore good 
> design principles

No, its not just "good foam" that is required, it is surrounding each
Headphone and each Human wearing them with an 80 dB Accoustic chamber to
solve the problem of the LightSquared Rock band in the room!

There are TWELVE or more orders of magnitude  (120 dB) between a nearby
transmitter and a nearby GPS receiver.  That is, the transmitter is
1,000,000,000,000 times stronger than the sensitivity of the nearby GPS
receiver.  It is absurd to expect every $20 GPS to have 120 dB filters.  

Ham radio only needs 40 dB out of band rejection to be within FCC specs.
NASA demands 80 dB out of band rejection.  LightSquared wanted every $20 GPS
MFR to install 10,000 times more filters than even NASA!

No, the analogy is correct.  That is why the FCC has always (when they had
real engineers anyway) had band plans that SEPARATE Transmit bands from
weak-signal satellite receive bands.  It is ludicrous to allow a bunch of
clueless lawyers try to buy their way into putting Transmitters in the the
RECEIVE ONLY satellite bands.


From: Robert McGwier [mailto:rwmcgwier at gmail.com] 
Sent: Wednesday, February 29, 2012 7:30 PM
To: Bob Bruninga
Cc: amsat-bb at amsat.org
Subject: Re: [amsat-bb] Lightsquared Analogy

On Feb 29, 2012 3:01 PM, "Bob Bruninga" <bruninga at usna.edu> wrote:
I finally figured out a good analogy about the LightSquared and GPS fiasco.

There is a "music room" where people can go and, with headphones, listen to
their own music.  No one disturbs anyone else.  Everyone is happy.

A LightSquared rock band comes into the room and begins to play at max
volume, and then insists there should be no problem because the headphones
work just fine in providing the isolation between what each person is
listening to.

Therefore the interference to everyone in the room is not their fault, but
the fault of the Headphone Manufacturers!


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