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<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>
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<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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