 I bought the Graupner IFS system which is the XPS system in the US, this was installed in my SebArt Angel, previously on a Spektrum DX7. The site I fly from has known interferance on PPM from what we belive are transmission towers on either side of the Thames, these interferance areas are in four place's on our site and are well known, PPM generally glitches when passing through them. The IFS system locked out in these four areas with the associated brown trouser responce, I had done a full range test proir to flying and have since tested the system on the ground in the same areas with the same results, at no time did the system go into fail safe, it just locked out for a second or so each time the Rx was in the appropiate area. In my opinion the IFS system is the same as flying on PPM, it locks out instead of glitching, from all of the US sites it seems this system does not hop to another frequency when experiencing interferance, Jim Drew who is XPS has been asked on many occasions to demonstrate the hopping of this system with no responce. Graupner have now given my supplier a credit note for this system. This is not meant to knock the system, but to inform all of its limitations on a highly interferance prone site. Mike
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I'am a big fan of 2.4 but as we have seen all the systems seem to have some problems, I had considered the XPS system first but after researching it on various forums there seemed to be a lot of unknowns about it and alot of questions the maker would not answer. I did think once Graupner had put there name that the system must be reliable but after reading you message I'am glad I went with the other system (I use Futaba and Spectrum depending on the models) with none of the issues you describe. Our site is in the middle of the city and I was concerned about all the other 2.4 devices using this band but 5 months on and I have had no problems.
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Absolutly, I also thought that with the Graupner name I was on a safe bet, I am now flying Spektrum exclusivly in my Futaba Zap without any problems, this was after getting the DX7 to test it out on my site. Mike
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I've flown the IFS and must say If not had a problem with mine. The single aerial is limiting and I know of a few people who have had issues so there must be something with particular installations. For sure the Spektrum system seems to be "idiot" proof and works well in all model types. masking of the single aerial is easy on the IFS Dave Wilshere
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Having used only dx7 2.4 for 14 months in everything from 72in glow to large petrol aircraft ,with other clubmates on various alternative 2.4 systems,no problems at all,exept it has not improved my landings!!  regards roy. ps, Dave ,the new JR sounds interesting.
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Dave Did you fly the IFS system on a PPM interferance prone site? Mike
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Mike
I wouldn't know about PPM, it's for boats!
Most interferance is below 300mHz so at 2.4 Ghz is should not be a problem Dave
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Dave I can't argue with PPM being for boats, but I was just interested if the area you flew the IFS in has any experience of PPM interferance, as it seems the IFS system does and goes into lock out when this occurs, my site is not PPM tolerant, I even went to the extreame of putting the Rx up inside the canopy of my plane to ensure that no servo or battery wires where anywhere near the antenna, but this did not seem to make any difference to the problem. Mike
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Mike I'd be very surprised if anything out side hits 2.4, the sort of interferance that causes 35mHz PPM to glitch would not touch 2.4, it's way too far up the band. I'd need someone with a better understanding of electrical interferance to comment. Dave
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Dave The transmission towers on either side of the Thames are broard band communication towers transmitting on all communication and information bands, the analogy with PPM was purly to point out that the area of transmission causes PPM interferance an is line with the communication towers it was not to allude to the fact that PPM is interfering with 2.4Ghz that was an assumption on your part. If you require any scientific evidence that 2.4Ghz can be hit by outside sources please go to the dedicated thread on RC Groups titled "xps To hop or not to hop (moved from XPS site)" there you will find extensive evidence of 2.4Ghz interferance and the investigations into the non hopping of the XPS system. XPS being Graupner IFS in Europe. Mike
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 Just to put my penn'orth in, I've yet to fly my 2.4 gear, but I have flown 459 for many years, in many places, and never had a single twitch caused by external rf noise, including in front of the big buckets on the BBC tv mast at Winter Hill, where my half a watt of rf would be well and truly swamped by the kilowatts of tv signal! It is just a pity that I cannot find anyone to service my receivers, which are suffering from old age.
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All my old receivers are fine, its me that needs the service.  Mike
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