Kevin,
According to the published information from Spektrum, their system divides the
2.4 GHz in channels, 80 I believe. Each time you turn on one of their systems
it finds two channels that are clear and establishes a link using those two
channels. If it loses link on one it uses the other. Of course link can be
reestablished with the first so that you have two again. There is no hopping.
Spektrum calls this Direct Sequence Spread Spectrum (DSSS) .
Based on this, Spektrum can have 40 systems running at one time. This system
was first introduced to the airplane market via the DX6 transmitter in 2005,
which was based on a JR 6 channel radio. Later Spektrum came out with the DX7
which was based on the JR 7202. Then they released and a variety of modules for
Futaba and JR transmitters.
Now JR has standardized their own brand transmitters on Spektrum 2.4 GHz
technology. Many of the JR 72 Mhz systems have 2.4 GHz dedicated counterparts
that use the Spektrum 2.4 GHz system.
XPS, Xtreme Power Systems, does not sell radios, only modules that go in a very
wide range of third party ground and air based systems. They divide the 2.4 GHz
band into some number of channels, 120 I think, and the radio/receiver establish
on one channel. They stay there until some kind of interference occurs, then
they hop to another channel. This is a hop on need system, for lack of a better
term.
Futaba makes their own brand of radios and modules for their brand of
transmitters. They establish a single channel and hop constantly. I have not
seen a spec on how many channels they divide 2.4 GHz into.
All three use a unique ID to establish an unique link between the transmitter
and receiver so that the receiver only listens to the transmitter to which it is
bound. Spektrum has taken this and created a unique feature called model match
that establishes a memory of which receiver is tied to which model memory in
their DX6i and DX7 transmitters. The JR transmitters have this too. It does
not work with their add in modules.
I hope that is helpful. You can find more info and more details at:
http://www.spektrumrc.com/DSM/Technology.aspx#howWorks
http://www.xtremepowersystems.net/
http://2.4gigahertz.com/
Best regards,
Ed Anderson
Date: Wed, 5 Dec 2007 01:01:38 -0600
From: Kevin O'Dell [EMAIL PROTECTED]
To: soaring@airage.com
Subject: Re: [RCSE] Spread Spectrum Differences
Message-ID: [EMAIL PROTECTED]
I guess my first question is you are a EE student and not an amateur
radio operator?
At any rate
802.11b, depending on the data rate, is probably direct sequence
spread spectrum..a good explanation of the differences can be
found in the ARRL Handbook for Radio Communicationsalmost any
version in the past few years will have it.
Kevin O'Dell N0IRW
On Dec 4, 2007, at 11:45 PM, Peter Klemperer wrote:
Hi,
I'm an electrical engineering student and I'm wondering what the
real technical difference is between the Futaba and Spektrum
systems. Anyone out there that knows the specifics or can point to
a resource?
From what I gather from the threads, the Futaba system uses some
sort of continuous frequency hopping but the JR only hops some of
the time? What would trigger a hop (perhaps a detection of
increased error rates)?
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