Independent tests prove lack of frequency hopping with XPS

[USN_POPS]

	Quote: Originally Posted by rede2fly
	dude you totaly miss the sarcasm. sorry my fault, my bad.. ill stick with blond humor next time. dont want to confuse anyone

I like humor as much as the next guy, but I feel that we all need to give the manufacturers of this new technology a break. I was around when Proportional came in and beat out Reed Systems, when we went from 27 Mhz to 72 Mhz, when we had so few channels that you could wait for hours for your turn on a frequency. In every advance there were problems. They were overcome and we moved on.

Prior to 2.4 and spread Spectrum, they had pretty well reached the peak of what could be done on the lower Freqs. And there will be growing pains here. The difference now is that there is the internet, and the forums to enable beating up on the manufacturers rather than waiting for the solutions.

I for one, and perhaps I'm the only one, have had nothing but good results with SS, and XPS at that. So it gets annoying when there are posts that are in most cases not based on facts, or the problems turn out to be not the SS system, but improper installation or failure of another component not related to SS.

I would like to see some positive statements, or just no statements if you can't be positive. Or Questions about things, allowing those with the answers to respond - again in a positive manner. If you have a situation with a system, discuss it, contact the manufacturer, dont just jump in and say the stuff is crap. Why do these forums have to be so negative??

This too shall come to pass, and there will be new technology to pick on someday.

[JimC-MD]

Did RC planes crash before 2.4G radios?

How many of those crashes were radio failure?

How many were mechanical failure? (electrical supply too)

How many were dumb thumbs?


I have seen a bunch of people go into lockout


between the ears. They swear it was something else.

I still see that nobody had answered my question.

zzzzzzzzzzzzzzzzz

[Kiwi]

Jim,

For sure there are a lot of lockouts between the ears that cause as many crashes as system failures. The point of this thread from day one was to tell people one system was not doing as it was claimed by the designer. That is XPS does not skip if the noise floor rises suddenly.

The carry on from that is we are no assembling all the test equipment to do some in field testing to simulate as close as humanly possible what happens to systems in these noisy environments. No one said there were no GUID´s etc but ASSAN´s first release did have GUID's so not all 2.4 Ghz stuff is what its supposed to be.

As for the noise I think there are some horror stories coming up as we learn from this technology and I am sure we will find locations that 2.4 Ghz systems will hard pushed to handle.

Sure it's early days yet with this technology but if you look at three of the players in the game, SPEKTRUM, XPS and FASST they have all made huge changes to the systems they produce in the last 12 to 18 months and I'm thats going to continue for a long time to come.

Those are changes dictated by field testing and people using forums like these to pass on the problem, try to find a reason and then hope the manufacturer picks up on it and fixes it.

Points such as the following. This happened last weekend at an event in Argentina.

The pilot in question is one of the best in the country by far and this is first hand.

They setup a new glow plane with a FASST 7 channel radio, new out of the box. Range tested it, done everything you would normally do. The plane took off, went 50 yards and started to roll. It never stopped and crashed. First flight. OK take everything out, test it and it all works fine. No reason for the lockout.

Do another range test on the equipment and when the guy walked 70 yards approx from the radio all was well, but as soon as he placed his body between the antenna and the plane the Rx light went red and into fail safe. Turn and face the plane, it went green again, turn away and bammo, lockout.

Radio is now on the way back to Futaba to see what is going on. But no GUID problems or noise problems. Just sheild the antenna with a human body and its all over rover.

I´m sure there are huindreds more learning experiences on the way for a lot of people. Its interesting times.

[JimC-MD]

I understand all that Kiwi. That is not my point.

The testing will be great, I am sure. HOWEVER.

Test must be conducted with a standard. What I asked days ago was if anyone had any information on the rules for use of this band. I do not give a RATS patoooie if XPS does not shift channels......... IF!!!!!!!!! it is the way the Video camera blasts out a link that is not following the rules. I do not know this, I am ASKING.

Yes, the CAPS are me yelling. Well, not yelling, let's call it emphasizing words. I am a methodical person that diagnoses problems every day. Before I can test, I need to know how it should work, what it looks like when it is working and what will make it not work. All I have EVER seen in these discussions for the most part are general statements, speculations and accusations. WHAT ARE THE RULES!?!?!?!?!

If there are no real rules or it is jungle rules, then we need to know THAT. If the rules were never intended to account for a link robust enough to entrust to what we do, we need to know THAT.

NO!!!! I AM NOT AN XPS FAN-BOY OR WHATEVER CUTE TERM YOU WOULD LIKE. DON'T HAVE ONE AND NOT LOOKING> SO IF THAT IS WHAT ANYONE IS THINKING GO AWAY!

Not directed at you Kiwi. Just a little tired of the B1^C# n moan threads. It always seems to get worse in the winter. You know, never let the facts get in the way of a good story..

[USN_POPS]

AMEN TO THAT!!!!!!!

If you can't say somethin' good - Don't say nuttin!!

[XJet]

	Quote: Originally Posted by RichardCorby
	It takes a flooding of the entire 2.4 freq range to cause any of the systems to quit.

Absolutely incorrect.

JR/Spektrum can be shot down by a reasonably strong interfering signal on both its chosen operating frequencies - even if the rest of the band is totally clear.

XPS can be shot down by a single interfering signal that suddenly appears on the single part of the spectrum it has chosen to operate.

FASST is a lot harder to knock down because you'd need to saturate a pretty high percentage of its 36 operating frequencies before you lost sufficient data packets to force a failsafe.

	Quote:
	And that is much more rare than is indicated in these forums.

How do you know this? What research have you done?

It's been my experience (in several years of 2.4GHz telemetry and control use on UAVs) that the 2.4GHz spectrum can become *very* busy from time to time -- largely depending on location and also altitude. Wandering around with a monitor or spectrum analyzer at ground level tells you pretty much *nothing* about what a model is experiencing at altitude. 2.4GHz is largely line of site and you only have to compare the view from even a few tens of feet of elevation to that at ground level to see just how many more potential noise sources become "visible".

The ground-based negotiation of channel selection is probably the weakest aspect of Spektrum and XPS systems. The fact that these systems work as well as they do is a triumph of technology over environment in many cases.

	Quote:
	No radio transmission is totally free from interferance at some time or another, and from some types of transmission. But Spread Spectrum is as close as we will get in my lifetime. And 900 GHZ is even more selective as I have read.

Yes, SS goes a long way towards mitigating the effects of interfering signals but not all SS is created equal (as we've seen).

A single frequency DSSS signal (such as XPS) is most vulnerable. A dual-frequency DSSS (such as Spektrum/JR) is more resilient and a hybrid DSSS/FHSS system (such as FASST) is by far and away the least likely to be affected by interfering signals.

SS is good, but it's not a magic bullet.

The worrying thing about current 2.4GHz technology is that manufacturers are betting that their SS technology will be a match for the sometimes incredibly high noise levels that are bound to occur on any "free for all" part of the RF spectrum. Mostly they are -- but sometimes they're not.

900MHz will definitely be better from the perspective of the physical attributes/effects of the RF signal. This means less multi-pathing, less troubles with unwanted signal blanketing, etc -- but the same issues will remain and some new ones will appear. It's possible (for instance) that there may be some issues regarding mobile phone use and 900MHz RC gear. If you're in the pits, leaning over your plane to adjust the engine, and your mobile rings -- will its signal swamp the 900MHz receiver that might just be a foot or two away?

What about cross-mod/intermod handling where there are perhaps multiple people talking on mobile phones in relatively close proximity to RC models on 900MHz?

What about the second-harmonic radiation from things such as car-alarm keychain fobs and other stuff on or about the 450MHz band?

What about the fact that 900MHz is far-less attenuated by distance -- meaning that the effective radius within which a signal may interfere with a model is greatly increased over 2.4GHz.

There's lots of stuff to still be discovered in respect to all RC systems on previously unused parts of the spectrum.

[XJet]

	Quote: Originally Posted by RichardCorby
	AMEN TO THAT!!!!!!! If you can't say somethin' good - Don't say nuttin!!

What a great idea -- let's hide our heads in the sand because we don't want to know the facts about anything.

How dare Ford or Chevy issue a recall when they discover a major fault in the brakes on their 2008 model -- if they can't say somethin good they should keep their damned mouths shut -- right?

Come on Richard, sensible people want to know what the strengths and limitations of the technology are even if you don't.

I would suggest that if you don't want to hear anything bad, you unsubscribe from all threads that have anything to do with RC technology because (since it's stuff designed and built by man) there are always going to be bad-news stories involved at some time or another.

[Flatlandman]

I took RichardCorby's comment to mean- if you dont have anything productive to say dont say anything-. This ideal I like a lot!

[Pale Rider]

	Quote: Originally Posted by Flatlandman
	I took RichardCorby's comment to mean- if you dont have anything productive to say dont say anything-. This ideal I like a lot!

Me too

[XJet]

	Quote: Originally Posted by Flatlandman
	I took RichardCorby's comment to mean- if you dont have anything productive to say dont say anything-. This ideal I like a lot!

If I misinterpreted his comments then I apologize.

[Flatlandman]

Im sure you didnt mean any thing by it; thats just the way I saw his comment. A lot of the time my diction doesnt match my meaning. It happens a lot on the net.

[JimC-MD]

OK XJet. Here it is STRAIGHT to YOU. What are the rules for 2.4 use? Does that video system you are saying knocks out the XPS conform to standards for 2.4? I am talking in the US. That is where I am so that is what I care about. Are there standards for 2.4? What are they? Do you know? If you do not and can provide us with no references I am through with this thread.

Hope you all would understand why.

GDay

[USN_POPS]

Wow!!! I'm getting scared to death of this radio control stuff. Nothing is going to save my investments in aircraft etc. All the technology is bad stuff. So I think I better give up this hobby that I've participated in for 40 plus years, and take up something safer.

Maybe knitting. Unless I stick a needle in my eye I should be safe.

[XJet]

	Quote: Originally Posted by JimC-MD
	OK XJet. Here it is STRAIGHT to YOU. What are the rules for 2.4 use? Does that video system you are saying knocks out the XPS conform to standards for 2.4?

What difference does it make?

If a commonly available 2.4GHz video transmitter (of which there are many thousands (or perhaps tens of thousands) sold and used world-wide every year is able to take out a system in the way I've observed, it's not really relevant if it's rule-compliant or not.

Walking up to some poor flier who's left with a pile of smoldering wreckage as a result of being shot down and saying "it must have been an illegal transmitter" isn't going to put that bird back together, replace the engine or restore a life that may have been lost if it took someone out on its way to oblivion. This is especially true if those flying FASST and Spektrum/JR continue to fly, apparently unaffected.

While it might be nice to dwell in a world where everybody lives by the rules and all the relevant standards are rigidly adhered to I think we have to be a little more pragmatic when large amounts of money and human lives are involved.

If someone's weighing up the various 2.4GHz options I think it's a safe bet that they'll be more likely to opt for a system that shows the highest-level of resistance to legal (and illegal) interference -- or have I got that wrong?

This is why we need some objective, comparative tests which subject each of the available 2.4GHz options to a range of controlled conditions designed to measure their resilience to variouis forms of interference. Having access to this information can only be a good thing.

	Quote:
	I am talking in the US. That is where I am so that is what I care about. Are there standards for 2.4? What are they? Do you know? If you do not and can provide us with no references I am through with this thread.

There are standards for 2.4GHz -- although they do tend to vary somewhat in different countries (namely power, spectral density, etc).

The point you raise however -- in respect to the legality or otherwise of an interference source, makes it very clear that one would be silly to rely on having those "standards" protect you. They won't stop you being shot down.

Just talk to JD about the numebr of completely legal 2.4GHz sources that can adversely affect all 2.4GHz systems (including XPS). There are definitely flying fields around where *legal* 2.4GHz traffic has made model-flying on this band either impossible or decidedly unwise.

So clearly, even when the standards are rigorously adhered to, there's no guarantee that a system won't be shot down -- simply because 2.4GHz is a bit of a "wild west" band where, so long as you adhere to the few rules there are, it's pretty much "every man/device for him/her/its self."

Although the goal is to ensure that all 2.4GHz equipment "plays nicely with others" the permutations of possible combinations has already reached the point where any practical proof is a physical impossibility.

[USN_POPS]

Xjet:

We have an old saying here in the Western US that dates back to the old Cowboy days.

"Theres no sense beating a dead horse"

So now that you have beat this subject to a quivering pulp please live up to another old saying.

"Leave sleeping dogs lie"

I just returned from flying maiden flights on my ACE 4-4o Bipe and 6 flights on my 4 year old EP Superstar with not a glitch on the XPS system. So quit trying to burst my bubble.

In my case perhaps another old saying applies. "Ignorance is Bliss"