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: [email protected] 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 Communications........almost 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)? > RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
