Independent tests prove lack of frequency hopping with XPS

[Costas]

Slightly OT wrt this thread but.....

We had one of my friend's helis go in the other day while it was only a few feet away from us. Basically the XPS system went into the so called 'Zombie' state from what we could conclude.

I verified the electronics setup on this particular heli after the incident (my background is in the electronics/RF field) and I can conclude that it was all A-OK as far as power wiring and DC voltage supply was concerned.

I am very confident that the incident is NOT related to any RF/Hopping issues but I have read a few posts on the XPS system locking out with exactly the same symptoms on a number of forums.

You can read more about the incident over here... LINK

[Julez]

Hi!

I read over at RCG that some guy named "Bruff" allegedly made tests in some avionics lab proving that XPS would hop. Does anyone know anything about this?

[ricoalonso]

	Quote: Originally Posted by Julez
	Hi! I read over at RCG that some guy named "Bruff" allegedly made tests in some avionics lab proving that XPS would hop. Does anyone know anything about this?

Yeah... what I can recall in one of the posts is that he had it tested by some co-workers at his work (at XXXXXXXX, if my recollection is correct). Problem is, noone who was directly involve with the test will comeout as to how they did the test to show it does what it claims it'll do.

Well, I can't even recall if it was said whether the test made was to prove that the system really does hop or if the test was made to verify if XPS is up to the task, RF-wise... anyways...

^R^

[tadawson]

	Quote: Originally Posted by ricoalonso
	Yeah... what I can recall in one of the posts is that he had it tested by some co-workers at his work (at <edited at request of ricoalonso>, if my recollection is correct). Problem is, noone who was directly involve with the test will comeout as to how they did the test to show it does what it claims it'll do. Well, I can't even recall if it was said whether the test made was to prove that the system really does hop or if the test was made to verify if XPS is up to the task, RF-wise... anyways... ^R^

Bruff's tests were to verify hopping, which he stated it did . . .

- Tim

[sweetpea]

He also did it at his place of employment..........and probably doesn't want it in the PUBLIC FORUM what company did the tests since it could get them and him in hot water for using equipment for personal use.

Does that mean it didn't happen? No, but no kidding proof is still requested by those against the system which is fine.

[Edge 540]

Did anyone stop by the xps booth at Toledo? (I saw a display; it might have been part of a larger booth) What is their official response about the elusive hopping in current and upcoming products?

[Flyfast1]

It does appear that many of those complaining about XPS are not XPS owners/users, so I am not sure what to make of that. There have been some documented crashes with XPS, but there have been many unexplained crashes with other 2.4 GHz radio brands as well, so I think it's difficult to draw meaningful conclusions from what we know. Some of these planes have complex systems with lots of single points of failure that make it difficult to determine the exact cause of a crash, especially if the plane is totaled.

I have been using the XPS system in several airplanes for over 6 months and am very happy with it. It enabled me to use all of the programming of my Futaba 9C without having to change anything. I have used it in one glow plane and several large gas engine warbirds. These planes are over 100" ws and have 75cc and 100cc gas engines on them. I did lots of my own testing in a small glow plane both on the ground and in the air with fellow pilots and we could not make it fail. That gave me a lot of confidence to use it in other planes and it's nice to not worry about others on my frequency.

One time I was flying a 1/4 scale ME109G (34lbs) on 72MHz and out of the corner of my eye I saw another pilot roll his glow trainer down the taxiway towards a flight station. I knew that this guy used my frequency only and I yelled to make him aware of the situation. He immediately make sure his transmitter was off and put it back in the impound area, but we might have narrowly avoided disaster and personal injury. I do not have to worry about this situation with any of the 2.4 GHz radios, including XPS.

	Quote: Originally Posted by KrisW
	Face it. . XPS has severe limitations. Those limitations make it something to be wary of. If you are truly conscientious and caring about your hobby, the limitations and problems associated with XPS will make you use another 2.4 system, simply to avoid the problems that so many people have encountered. NOT doing so, especially in very large or fast aircraft, is IMHO extremely irresponsible.

It does seem that if XPS does not change channels when interference occurs on the current channel that it would not be as robust as the Spektrum or Futaba solutions. The threads (especially XJet and others) have done a good job of educating us about how these systems work. What I think would be useful is an discussion of what the significance of the differences are in practical terms. It's interesting to discuss the differences between the systems, but what is the significance of the differences? Are they significant for the typical flyer at the typical field, or are the differences only going to matter in extreme circumstances? I think the discussion should also take into account the retransmission capability of XPS that other systems do not have. At least theoretically this should reduce packet loss, but it's hard to know.

-Ed B.

[Cherokee Jim]

Hello All,

Nothing is confirmed until it is measured!

The problem that the current crop of 2.4GHz systems are complex and difficult to measure.

I read enough success reports on the XPS system to have bought it, I will continue to test it. One thing that I like is the ability to down load updates. No product is beyond improvement!

For as long as I can remember "I ain't Got It" just before a crash - many pilots will never admit that they were in error, piloting error, building error, setup error, or taking care of there of their equipment properly.

Some folks have had bad luck and some have been problem free - Why? I have to see the results of real measurements and testing - Again - Mr. Drew - we need an inflight data recorder to track fadouts, loss of signal, frame losses, voltage, signal strength .....

It would be very nice if all of the makers of 2.4GHz systems published the the techniques that they use to test their systems!

Anyone who publishes test results should also include information on their test setup so others can try to repeat the test.


Happy Flying,
Cherokee Jim Mahoney

[dick hanson]

Dang- I GOTTA do a "ballad of the XPS"
maybe in G- kinda Ramblin Jack Elliot style --

[Edge 540]

It would be huge "hit". Oh the irony!

[XJet]

	Quote: Originally Posted by Cherokee Jim
	Hello All, Nothing is confirmed until it is measured!

If only someone could get this across to Jim Drew -- in respect to frequency agility and antenna radiation patterns.

There are many claims but no substantiating evidence and when carefully measured independent evidence is presented that challenges the claims of XPS, its veracity is questioned by JD.

I fear that the lack of credibility demonstrated by JD is one of XPS's biggest problems.

[NormS]

Kiwi, can your test setup determine if Spektrum transmits simultaneously on the two selected channels or if it alternates back and forth between them?
Thanks a lot.
-norm

[BaldEagel]

	Quote: Originally Posted by Cherokee Jim
	Hello All, Nothing is confirmed until it is measured! The problem that the current crop of 2.4GHz systems are complex and difficult to measure. I read enough success reports on the XPS system to have bought it, I will continue to test it. One thing that I like is the ability to down load updates. No product is beyond improvement! For as long as I can remember "I ain't Got It" just before a crash - many pilots will never admit that they were in error, piloting error, building error, setup error, or taking care of there of their equipment properly. Some folks have had bad luck and some have been problem free - Why? I have to see the results of real measurements and testing - Again - Mr. Drew - we need an inflight data recorder to track fadouts, loss of signal, frame losses, voltage, signal strength ..... It would be very nice if all of the makers of 2.4GHz systems published the the techniques that they use to test their systems! Anyone who publishes test results should also include information on their test setup so others can try to repeat the test. Happy Flying, Cherokee Jim Mahoney

Firstly Cherokee Jim Please reduce the size of your font, you have been asked before not to shout.

Flyfast I

I am an owner of the system and I did not loose an airframe even though it locked out four times in flight, there are lots of dissatisfied owners on this site, comming onto the site and saying most people complaining are not owners is misleading and incorrect, please do not make statements that you can't substantiate, it does not help the case for either JD or this group, it just makes browsers who come onto the site think that this is a load of rubbish and do not read any further, or perhaps that's your intent.

I have tested the system as best as I can, my conclusion is that the system is only as good as a PPM system without the facility to fly through a glitch, because it locks out for a second or so if it swamped by interferance. Nothing technical about my testing, just an installation in a plane and tested on my flying site against PPM, PCM, 2.4 Spektrum and 2.4 Futaba, none of the others suffer interferance or lock out or fail safe, the PPM did glitch, only the XPS/Graupner IFS system kept going into lock out in the four positions on site that are none to be interferance lanes in the sky.

Mike

[KrisW]

	Quote: Originally Posted by BaldEagel
	Firstly Cherokee Jim Please reduce the size of your font, you have been asked before not to shout. Flyfast I I am an owner of the system and I did not loose an airframe even though it locked out four times in flight, there are lots of dissatisfied owners on this site, comming onto the site and saying most people complaining are not owners is misleading and incorrect, please do not make statements that you can't substantiate, it does not help the case for either JD or this group, it just makes browsers who come onto the site think that this is a load of rubbish and do not read any further, or perhaps that's your intent. I have tested the system as best as I can, my conclusion is that the system is only as good as a PPM system without the facility to fly through a glitch, because it locks out for a second or so if it swamped by interferance. Nothing technical about my testing, just an installation in a plane and tested on my flying site against PPM, PCM, 2.4 Spektrum and 2.4 Futaba, none of the others suffer interferance or lock out or fail safe, the PPM did glitch, only the XPS/Graupner IFS system kept going into lock out in the four positions on site that are none to be interferance lanes in the sky. Mike

Mike. . Cherokee Jim isn't actualy shouting .. he's just making his presence felt. Shouting involves using all capital letters, and lots of exclamation points. . .

Actually, I find his font refreshing. . it's much easier to read compared to the blur I usually see on the screen. . yes, I HATE reading glasses. .

[BaldEagel]

	Quote: Originally Posted by KrisW
	Mike. . Cherokee Jim isn't actualy shouting .. he's just making his presence felt. Shouting involves using all capital letters, and lots of exclamation points. . . Actually, I find his font refreshing. . it's much easier to read compared to the blur I usually see on the screen. . yes, I HATE reading glasses. .

Trouble with that is if we all did it the pages would only have a few posts each on them.

Mike