country flier Posted November 22, 2007 Share Posted November 22, 2007 David, The advent of the 2.4GhZ systems certainly brings some interesting applications, whether from Specktrum, Futaba, JR or whomever. When Spektrum announced the AR6000 about two years ago I bought one and saw the future. These new AR rx systems only reinforce that view. My older 72MhZ systems (U.S.) will be used in some models until they're "done" but they won't be replaced, only supplanted by 2.4GhZ. Harold Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted November 22, 2007 Share Posted November 22, 2007 Yes Spektrum aren't hanging about at the moment Harold, they have quite a receiver line-up now. Quote Link to comment Share on other sites More sharing options...
country flier Posted November 23, 2007 Author Share Posted November 23, 2007 Indded David; the range accomodates virtually everything from indoor to park to full on models. I imagine one day they will use the telemetry functions found in the surface versions for cars resulting in a fully contained system with all of the control and feedback elements one could want with precise control. Naturally no system (full scale or model) is 100% "bullet-proof" but the improvements with digital technology are there. It worked for Lockheed with the SR-71 and U2 over twenty years ago so here we go with similar progress in the modeling world.Harold Quote Link to comment Share on other sites More sharing options...
Alan J Roberts Posted November 30, 2007 Share Posted November 30, 2007 I can't help wondering why Spektrum seem to need a satellite unit, when Futaba are able to pack everything into a very nice single unit?The fact that this new larger Spektrum receiver now supports up to four satellites raises a further doubt in my mind about their confidence in their single satellite's system's reliability?I'm not slagging off Spektrum or JR in any way, I've been a user of those systems for many years and have always been happy with their reliability. Its just a question that I feel needs to be answered.AJ Quote Link to comment Share on other sites More sharing options...
Les Adams Posted November 30, 2007 Share Posted November 30, 2007 My understanding is that it is to ensure that there is a line of sight connection between the TX and the RX. With 2.4 Ghz even an engine is enough to block the signal. By having lots of satellites in different positions ensures that the signal gets through. Futaba's approach is to put the short 2.4 Ghz aerials on the end of a short length of coax (e.g. only the end bit is the aerial) ensuring the two aerials are far enough apart and with a different perspective again to allow a signal gets through. My guess is that the approach with the +2 or more aerials for the AR9100 is just added fault tolerence.Les Quote Link to comment Share on other sites More sharing options...
country flier Posted December 1, 2007 Author Share Posted December 1, 2007 Les hits on the point there. The physical size of larger components can effectively shield the radio waves in the 2.4GhZ range. Thus the utility of the satellite antennae is to provide a means of always having an antenna unblocked to receive a signal. Added fault tolerance equates to redundancy. Also the later Spektrum systems are considered full range which means beyond visual while the radiated power of the signal remains the same. Antenna performance then takes on an added dimension; the satellite redundancy in large models provides that performance.Harold Quote Link to comment Share on other sites More sharing options...
Alan J Roberts Posted December 5, 2007 Share Posted December 5, 2007 I appreciate what you are saying there guys.Seems to me everyone's quoting what they've read in the manuals and mags?I wonder if anyone out there in the real world has experienced glitching with their Futaba radio's which they put down to loss of signal. I certainly haven't had any with my Futaba stuff?AJ Quote Link to comment Share on other sites More sharing options...
Former Member Posted December 5, 2007 Share Posted December 5, 2007 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Alan J Roberts Posted December 5, 2007 Share Posted December 5, 2007 A very good point Eric.I'm assuming that even on a large model with four satellite receivers deployed surely its unlikely that any of those aerials would be working once they were all behind a tower?I'm doing my very best to justify these satellite receivers here guys, but I'm having real difficulty . . . Quote Link to comment Share on other sites More sharing options...
country flier Posted December 5, 2007 Author Share Posted December 5, 2007 Alan,I'm in a rural area and have never had difficulties with various radio systems related to the technology, whether 72Mhz or 2.4Ghz. Perhaps you could expand on your concern with the satellite receivers? Harold Quote Link to comment Share on other sites More sharing options...
Alan J Roberts Posted December 6, 2007 Share Posted December 6, 2007 Hi Harold,I'm not concerned about satellite receivers, I'm sure that they work very well.I am trying to convince myself that they are actually required. My reasoning is that Futaba don't seem to need them?bestAJ Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted December 6, 2007 Share Posted December 6, 2007 Although the Futaba system receivers have longer aerials of course ... Quote Link to comment Share on other sites More sharing options...
country flier Posted December 7, 2007 Author Share Posted December 7, 2007 Hi again Alan and Dave,The antenna question may be resolved by looking at the means Spektrum and Futaba use to avoid "signal collision" which is required by internationally agreed upon 2.4GHz standards.In the case of Spektrum their DSSS (direct sequencing)system employs two seperate frequencies-with two receivers- used for the duration of the flight or run. This is also a broadband approach which favors low power transmission. Embedded software on the chip then selects the frequency with the best signal for processing data. The frequency shift, narrow band approach of the Futaba system selects a single 2.4GHZ frequency every 2ms or 500 times a minute. Embedded chip software then determines which antenna has the best signal. Both systems seek to have a reliable signal but use different methods to achieve that. Installation-wise the Futaba might be easier to use.One interesting item I found in searching is that metal and carbon fiber can really attenuate a 2.4 GHz signal which has a wavelength of about 12.5cm or just under 5". Thus the antenna placement could be a critical item.Thanks for piquing my interest.......Harold Quote Link to comment Share on other sites More sharing options...
Alan J Roberts Posted December 7, 2007 Share Posted December 7, 2007 Hi Harold,That's an excellent piece of information. Probably the answer that I've been seeking.I'd like to know your source of info on the carbon fiber attenuation so I can follow that up myself.If the carbon fiber issue is as significant as it sounds it would certainly enhance the case for purchasing the Spektrum system over the Futaba one?regardsAlan Quote Link to comment Share on other sites More sharing options...
country flier Posted December 7, 2007 Author Share Posted December 7, 2007 Hi Alan,I think the Spektrum would have the advantage there but in any case the antenna must be unblocked re: the radio wave.Carbon fibre is electrically conductive and thus can attenaute a signal; Peter Christy writes on some 2.4GHz issues in the Bentley Flyers at Crewe, Cheshire. They are BMFA club no. 0322. regards,Harold Quote Link to comment Share on other sites More sharing options...
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