Independent tests prove lack of frequency hopping with XPS

[ricoalonso]

After reading most of the posts (both positive and negative in both RCG and FG) regarding XPS, I honestly think (my opinion, of course) that the only advantage (at present) of XPS over 72Mhz is that the pilot does not have to check the frequency board before he/she turns ON his/her Radio system.

^R^

[Wojcigitty]

	Quote: Originally Posted by Wojcigitty
	Yes, it is able to coexist on the same frequency as another 2.4 ghz device, and it is a lot "smarter" in how it's bound receiver-to-transmitter. However, it's to be expected that, out of nowhere, another device could start broadcasting on the same frequency as XPS and use up all available bandwidth. FASST and Spektrum have methods of dealing with this. It's NOT expected that all of a sudden another device could suddenly take a single frequency on 72 MHz without warning. 72MHz systems are not designed to be frequency-agile, and when properly used (frequency control is implemented), they do not need to be. 2.4GHz systems ARE supposed to be frequency-agile, and even when used properly, they DO need to be.

I would still rather use 72 over XPS.

[aviti]

If something sounds too good to be true, it probably is. I've thought that since the first time I heard XPS's claims and it sure seems to be correct in this case. Oh, and by the way XPS cheering section, there are other valuable threads on this site other than the XPS ones, might be worth checking out...welcome to the site.

[Julez]

72 relies on the frequency to be very clean. There is no other equipment on 72 other than RC radios, so the frequency is usually clean, unless someone shoots you down, that is.
2.4 relies on the ability of the reciever to cope with a lot of noise. We are not the only ones on 2.4, but this is usually not a problem, als most 2.4 systems can cope with interference very well due to antenna diversity and frequency agility.
If a 2.4 system now lacks both these features, 2 of the main advantages are gone, making this system a lot less safe.
Therefore, I tend to agree that a decent dual conversion PCM 72 system is superior to XPS.

[ricoalonso]

Agree, and you said it better Julez, for the average pilot to understand the current situation.

Thanks.
^R^

[JEFFRO503]

	Quote: Originally Posted by BaldEagel
	Ian Being in the UK we fly on 35Mhz, the field I fly on has proven RF interferance problems, PPM gets glitches in approx four different areas of the site, these have been mapped as being in line with communication towers on either side of a large river adjacent to the site, these towers are not in sight of the flying field, when I installed my Graupner IFS system, this is XPS in Europe, I experienced lock out in the same areas that produce glitches for PPM, this to me proves that the IFS/XPS sytem does not hop to a different frequency when experiencing interferance which is what I understood it would do from the advertising for the system. The main reason for being on this site is to accumalate sufficient information to allow an informed and weighted responce to Graupner who at this time refuse to reinburse me, however, the Trade Descriptions Act in Germany is more stringent than in the UK and I am hopefull of a succesfulll conclusion. Mike

Oh holy hell!! Until now , i didn't know Graupner and XPS we're the same unit. I haven't read much good stuff about this system either......that explains it.


And mike , i wish you the best of luck with getting some money back for whatever aircraft you lost due to this system.


I really hope for JD's sake , that if and when he comes out with that new 900mhz system , it works really good , and the way it is supposed to. If he can get the system to hop and stay linked up , i think he'll have a good system at a competitive price.

I know he'll never admit that the XPS system that's out now has a major flaw in it , but it would be nice to see him make good on a new system. I think he could save a lot of face and less lawasuits this way. I really , really hope that one of these aircraft don't lock out at the wrong time , and hit someone , possibly causing serious injury or death. Is it worth it i wonder??....i think not.

[JEFFRO503]

	Quote: Originally Posted by Julez
	72 relies on the frequency to be very clean. There is no other equipment on 72 other than RC radios, so the frequency is usually clean, unless someone shoots you down, that is. 2.4 relies on the ability of the reciever to cope with a lot of noise. We are not the only ones on 2.4, but this is usually not a problem, als most 2.4 systems can cope with interference very well due to antenna diversity and frequency agility. If a 2.4 system now lacks both these features, 2 of the main advantages are gone, making this system a lot less safe. Therefore, I tend to agree that a decent dual conversion PCM 72 system is superior to XPS.

Thanks for putting that into lamens terms for me Julez!! I don't understand how all the 72mhz , and 2.4 stuff actually works , but i can say , from reading through this entire thread , i have learned a lot. Now....i can't remember a lot of the "high tech stuff" , but at least i try to hehe.

[chewy]

	Quote: Originally Posted by Julez
	72 relies on the frequency to be very clean. There is no other equipment on 72 other than RC radios, so the frequency is usually clean, unless someone shoots you down, that is. 2.4 relies on the ability of the reciever to cope with a lot of noise. We are not the only ones on 2.4, but this is usually not a problem, als most 2.4 systems can cope with interference very well due to antenna diversity and frequency agility. If a 2.4 system now lacks both these features, 2 of the main advantages are gone, making this system a lot less safe. Therefore, I tend to agree that a decent dual conversion PCM 72 system is superior to XPS.

Julez,

Actually, from what I have read so far, it appears to me that SS systems has a few more advantages to help cope with other users on the same band

1. The spreading of the signal itself (as long as the channels used are not swamped)
2. The unique ID code (doesn't help if the channels used are swamped)
3. The time division routines and look-ahead (if implemented)


If the channels used are swamped then not matter what is used, the plane will crash, unless it has the frequency agility to get itself out of the way of the noise source.

So, actually 2.4 is a LITTLE bit better than 72MHz or 35 or etc, FM sets. FM cannot take much of ANY interference, whereas 2.4 is able to survive SOME interference.

chewy

[wrightme]

	Quote: Originally Posted by BaldEagel
	I did not say you should not be here, I just asked why you where and so late in the day, I am here because my Graupner IFS system kept locking me out in flight and plainly just does not do what I was lead to belive. Your view as mine is biased not ballanced. Mike

"Late in the day" is only relative to the time zone of the poster.

My view is open. I see shortcomings in the XPS system, but whether you want to believe it or not, it is much easier to provide a proof of something like an XPS hop than to provide a disproof. We have seen specific test instances where it does not hop; specifically with a noise source similar to 2.4 Ghz systems for RPV. I do see that such a noise source will cause a big problem for XPS, and that the tests seen so far DO prove that it will not "hop" away from such a source.

I fly out in the desert, and nowhere near such noise sources. It really does work for me, in several different airframes. The big problem I see in the RCG Vendor forum is that the "hop/no-hop" "discussion" ends up obliterating any hope of actual XPS users receiving any help from others about their installations and use. Invariably, someone who does not like XPS (or doesn't like JD, or claims, or...) sea-lawyers the information into submission. There are plenty of forums for that discussion. JD can run his vendor area the way he sees fit.

Those who "bash" XPS then belittle those who choose to use it. This does not help the hobby in any way at all. I once again contend that no matter which R/C system you choose for your aircrafts, each time any of us puts a model in the sky, there is a chance that control will be lost (for MULTITUDES of reasons), and a crash will ensue. The best course of action is to always fly in an area and in a style that does the best to minimize the impact of an impact.

Each system I see has SOME level of "flaw" that people experience. Choose which you wish, and fly. I do.

Biased? If you check back a page or two, you will find that I have posted that I am seriously contemplating going to Spektrum. I see that the two channels is more robust than one channel, and that multiple RX modules can provide fewer blind spots in an installation. If XPS comes out with telemetry and/or daughter RX modules prior to that, my decision will be much more difficult.

[socalsal]

You ask why do something that obviously puts you at RISK??? We all do it every single day we are alive. If you drive a car you are at risk etc. This I think you can understand right?? I hope so.
72mgz systems are still getting "blamed" for all sorts of crashes. 2.4 will be the same till something else comes along. Then it is that system. I'm no radio guru by any means but just because on person did his very best to get XPS to hop and could not does not mean the system is worthless....not yet. We need to have more tests in different ways to prove that this XPS thing is a bad piece of hardware.
I find it very hard to believe that the AMA is not aware of this problem and has not done anything to stop its use at ANY AMA field. Think about it?? if this XPS or any other system is that bad it should be banned just for the liabilty factor alone. Tell me is the AMA aware of this??? I sure has heck don't know if they are.
I fly both XPS and Futaba systems on 2.4 have not had problems with either as of now. After reading this forum about XPS I may be thinking of it more when I fly it. But so far so good. Yes I do do things that put me at risk...like going to war and KNOWING it could get me killed or driving on the roads or climbing aboard a full scale plane etc.
O.K. I'm done.I'm not a JD fanboy as some have put it.don't even know JD or any of you folks here for that matter. But it sure seems that if someone gets on this forum and does not agree with the folks that dislike this JD fella then they are all idiots as well. Just goes to show you how funny people are.

	Quote: Originally Posted by buttface
	The system is still usable of coarse but should only be limited to foamies that you don't care about.Even then then it not the best for them either.I don't understand why lots of people are still using it in there glow planes and giant planes after knowing about all of the bad stuff with XPS. They continue to fly ticking time bombs and stand up for the product.But then people do dumb things every day and I for the life of me cant figure that out either. I read the local paper today .A man parked his car in the middle of rout 7 bridge and jumped plummeting to his death.I wonder If he was trying to prove every one wrong that told him he couldn't fly.The XPS users just keep using it hoping to prove it works for them.Why do something that obviously puts you at RISK ???

[adjonym]

The one thing i have problems understanding is; How can someone that bought a XPS system defend it?
Let me explain what I mean.
If I bought a car, a nice shiny car that's advertised to have a nice powerful V8 engine, a 5.1 stereo system, nice leather seats and beautiful alloy wheels. Then on delivery you get a car with a 4 cylinder engine, a mono AM radio, and cloth seating. Following the logic of the ones defending XPS, I still should be satisfied.
Why?
Well, a cars purpouse is to take me from point A to point B. A four cylinder engine will do that just as good as a V8.
A stereo systems purpouse is to deliver sound. An AM mono radio will do that.
Leather seats are just there for you to sit on, any old cloth will do just fine.

My point is; You aren't getting what you payed for, as advertised.
It's impossible for me(not owning an XPS system) to understand that ANY customer is satisfied when they havent' got what they payed for. I'm still amazed that the company haven't been sued.

Again, any results that cant be reproduced DOESN'T EXIST!!!
I said in an earlier post that i was close(well, i had decided to) buy an XPS system, based on performance(advertised) vs price. Everytime I read a post there I feel lucky to have read all the CONFIRMED tests, that changed my mind. Still makes me angry that I got so close to being ripped off.

[ss40]

	Quote: Originally Posted by 1bwana1
	All the XPS stuff aside, we should welcome the new posters to the FG site. I hope they spend some time, and join in some other discussions. We have a great community developing here, and everyone is welcome. Thanks for stopping by guys!

A little late but I need to say this. Re: your comments:
Certainly better than the other posters "attitude". I fly models in the hundreds range not thousands, but my knees shake more during a maiden than some of the guys who fly the larger. As a result of being here I am sorely tempted to get one of the Lanier 94", so your attitude about new guys is the right one.