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<DIV>I once calculated that we should be able to get 30 systems working in a one
MHz band. That would yield 2400 operating in the 2.4 GHz band. Seems
like the Spectrum should be better than advertised but who knows? Maybe it
is and they are being conservative.</DIV>
<DIV> </DIV>
<DIV>Jim</DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=geobet@gis.net href="mailto:geobet@gis.net">george w. kennie</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, February 23, 2007 10:51
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] SPECKTRUM
Modules for Futaba and JR</DIV>
<DIV><BR></DIV>
<DIV>It sounded like XPS advocated an almost limitless number of simultaneous
operational systems capability based on random channel coding.</DIV>
<DIV>G.</DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=joddino@socal.rr.com
href="mailto:joddino@socal.rr.com">J.Oddino</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, February 23, 2007 1:40
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion]
SPECKTRUM Modules for Futaba and JR</DIV>
<DIV><BR></DIV>
<DIV>I'm having a real problem understanding what an "unused frequency"
is. First of all nothing that transmits information transmits on one
frequency as it must use a band of frequencies. SS intentionally uses
a wide band of frequencies and the wider this band is relative to the
information bandwidth the more processing gain you get and that is
good. The Direct Sequence system "chips" the baseband information at
some high rate with a pseudo random code that should be unique to your
transmitter in order to spread the bandwidth. With different
codes it should therefore be possible to operate many RC systems
simultaneously using the same band of frequencies. </DIV>
<DIV> </DIV>
<DIV>Now getting back to "unused frequencies" , which we will interpret
as unused channels about one megahertz wide, what happens if a system (not
necessarily an RC system) that uses Frequency Hopping turns on and
spreads its info over more than one channel? Or just decides to use
the same channel that you are using? Maybe the FCC rules
prohibit this but I'd hate to depend on the government to make sure my
airplane doesn't get shot down. I've got to believe that "unused"
really means that the ambient noise level is below some acceptable value and
I'd like to think we can really operate a lot more than 40 users in an 80
MHz band.</DIV>
<DIV> </DIV>
<DIV>It sure would be nice to get an understandable, but more technical
description of this system and its limitations.</DIV>
<DIV> </DIV>
<DIV>Jim O</DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=JonLowe@aol.com href="mailto:JonLowe@aol.com">JonLowe@aol.com</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">nsrca-discussion@lists.nsrca.org</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, February 22, 2007
7:26 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion]
SPECKTRUM Modules for Futaba and JR</DIV>
<DIV><BR></DIV>
<DIV>
<DIV>
<DIV>In a message dated 2/22/2007 6:52:04 PM Central Standard Time, <A
href="mailto:patterndude@tx.rr.com">patterndude@tx.rr.com</A>
writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid">
<DIV><FONT face=Arial size=2>What does Spectral capacity - 40 systems
mean? Is this the number of tranmitters that can operate in range
of each other, or is this 40 channels or what?</FONT></DIV>
<DIV><FONT face=Arial size=2>--Lance</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV></BLOCKQUOTE></DIV>
<DIV>This is grossly simplified, but the 2.4 ghz band has about 80
frequencies. Each Spektrum unit picks two unused frequencies and
transmits on both. 80/2=40 transmitters that can operate at
once. It is a requirement of the FCC that things on this band don't
interfere with each other, and transmitter power is strictly regulated,
therefore anything using the band has to check before transmitting.
You have no idea which two frequencies you are on (nor do you care), as
they change each time the transmitter turns on.</DIV>
<DIV> </DIV>
<DIV>I've flown my Dad's Arresti III with the DX7 extensively.
Absolutely solid link, with no fear of getting shot down. I have
been waiting for something like the modules so I could use a decent
transmitter for things like throttle curves, conditional mixes, etc.</DIV>
<DIV> </DIV>
<DIV>I don't want to be at a field that has 40 airplanes in the air at
once!</DIV></DIV>
<DIV> </DIV>
<DIV><FONT size=2 PTSIZE="10">Jon Lowe<BR></FONT></DIV><BR><BR><BR>
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