Independent tests prove lack of frequency hopping with XPS

[RMaia]

	Quote: Originally Posted by KrisW
	I'm guessing this is one of the reasons 2.4 was picked by Spektrum, and why everyone else felt compelled to follow along in copycat fashion. Also the original equipment was meant only for foamies, and they wanted to get radios on the market that would not interfere with the 72 mhz stuff, so that the modelers could fly anywhere, any time, they wanted to. Great for Foamies, that fly in close. . not so great for $8,000 IMAC birds that are 2000 feet out in the middle of a roller. There were even discussions about how it's a really BAD idea to try to use a DX6000 for a gasser, due to limited range and other considerations. Back then I did it, with an 84" plane, just to prove it could be done, and I had no problems for the 10 test flights I tried it, but things have changed since then, and I have not done it since.

That makes a lot of sense to me!!

If the original intention was indeed just for foamies and park-flyers, it makes absolute sense to use the 2.4 spectrum. People tend to fly these models without much care to frequency control, heck, when I'm flying my foamie in the backyard I don't go running through all the houses in a mile radius asking which frequency they've got.... If someone, half a mile away also decides to fly their foamie in their backyard and happens to be on the same freq as me (72), we'll both have trouble.... With 2.4, this would be a non-issue.

The 2.4 "quirks" seem to be much less "drastic" on park-flyers and foamie, which generally are flown much closer in, lower and slower, allowing for greater signal strength and less "noise seeing". Also, if you have a lockout on a foamie, you've only got about $50 (or less) of airframe at jeopardy (I've never seen a foamie crash which resulted in a total loss of all equipment, including motors and radio....)....

Now, as it seems most of the world follows the "nothing's created, everything's copied" saying, instead of doing research for a new band more suitable for the larger, more expensive, higher flying and further reaching models, they've apparently just "blown up" the 2.4 concept from the foamies to the largers models.... And the problems are showing up....

[buttface]

	Quote: Originally Posted by KrisW
	Okay, 2.4 is looking more and more dangerous. . for whatever reasons. . increase in signals and interference above 50', stray "badly tuned" 2.4 systems floating around, the frequency hopping features not being as good as they seemed to be. . more and more big corporations using 2.4 and taking up more bandwidth. .. . . 900mhz is looking okay. . for now, but it's only a matter of time until it gets overused/abused, right? 72 mhz works, but you can get shot down by people ignorant of the frequency pins, or other stuff on the 72 mhz band 27 is truly dangerous. 5.8 ghz has an even shorter range than 2.4 Control line can get shot down by a frayed wire. Free Flights sometimes just fly away. . There's a lot of money, time, effort, and research being done to make our hobby, and our tenuous radio links, better. I'm sadly shaking my head in disbelief that no one seems to have finally produced the magic pill that will resolve the problems of interference and glitches. Just look at this thread . .tons of posts, and no one has the answer, but all that appears is more and more questions and doubts. I'm thinking of developing a neural interface helmet, that uses boosted telepathic signals on the Terahertz range to link to a borg receptor on the aircraft. That way, the only possible lockouts are from my own brain. Someone said that still happens. . may as well make it the ONLY way it can happen. But seriously. . anyone else have any bright ideas on how to solve all the problems? I certainly don't, but thanks for all the gret information, that has made me even more doubtful of technological innovation. I'm actually kind of depressed that all this effort, and money, and time, still has not solved the problem in a satisfactory manner.

I'm with ya bro. GOOD RIDENS!!!

[JimC-MD]

	Quote: Originally Posted by RH1N0
	Not sure why you persist with complaining on this thread when 5 seconds on google will provide the info you seek. But I can understand why someone would avoid answering the question on here since their response is likely to be thoroughly scrutinised etc. I suggest you start here and do some reading: http://en.wikipedia.org/wiki/ISM_band. Then perhaps you could summarise what you have learned from your research and post any specific questions you may have. No offence intended - just a friendly suggestion

If you see my posts as persistent complaining, you have misunerstood or I have written poorly. For my part, I will apologize if I have written poorly.

I have spent time researching and keep coming up with the type of general comments like are found in the link you provided (which I had already viewed)
What I take from those words is that we are interlopers on the 2.4 band. Priority goes to critical uses and they can shout on the band with approval. We are required to shut up and take it. Those are laymans terms to clarify my understanding of how it works. So that means to me that any discussion of the weakness of these types of com links should include the reality that unless we have a dedicated band where we are the ones that get to "yell" on the band and everyone else has to shut up and take it, we will always be subject to potential link failure. End of story. I think that is important to understand.

The reason that I have persisted in asking these question here is because of what I think the net is useful for as well as how I think helpful dialog takes place. We should be aware of the realities behind the scenes before we start pontificating. Some people are there, it appears, but they cannot assume that the average reader of these forums is.

I was told straight up by a person involved with UAVs that they ONLY use 2.4 for telemetry and not for control uplink. I had not seen that written that clearly in the past. For me it was a telling comment. I will let that expert make the comment themselves if they so chose just in case I misunderstood anything in the short conversation.

Not complaining, Just trying to raise the level of the conversation from speculation to documentation. My perception of a lot of these threads is the level of vitriol that develps is high.

I am not assigning that to Xjet. I think Bruce has a lot to add to this conversation as time moves forward. He is in the business of working with and around 2.4G. He is not a shill for any radio company. He has a lot more of the technical information in his head. My only effort here was to try to pull up any and all of the potentially unpleasent realities of this band. It may effect choices that are made. Information is power. The problem that developed very quickly in this thread it the good old "I want it NOW attitude" that causes so many problems to crop up. Really good testing takes time. I will wait for more to come out. Some may be more able to absorb potential risk than others and they tend to be the pioneers. People with less ability to absorb the risk may take a chance and then be really unhappy when it is not what they expected.

People hate to think they may have made or are thinking about a choice that may be less than ideal. It is the equivalent of calling someone stupid. They will lash out. That does nothing for good dialog. There are ways to call someone ignorant and have them smile and say thank you. They feel educated instead of berated. It is a fine line. I prefer to be educated, how about you? (that is collective, not at you Rhino)

The difference between manipulation and motivation is if you get caught

I am done with this until the testing starts to come in. Thank you Xjet, Kiwi and others that are taking time to do this. I am a diagnostician by nature and trade as well as a teacher. I wish I had the equipment and knowlege to get into this myself. How much is a ticked to NZ? hehe

[buttface]

Alright, pack it up now JD....Its all over now.The truth is out!
Futaba FASST is what I will be using.

[XJet]

	Quote: Originally Posted by KrisW
	On the other hand, concerning International attention on the subject, some countries do RC on their own assigned frequencies (35 mhz?), so engineering transmitter modules and receivers for yet another frequency band (like 500 mhz)that is not truly Internationally recognized as being set aside for RC ONLY would not be financially feasible, or advantageous. 900m and 2.4g are internationally recognized, making it a lot easier for the RC radio companies to jump right in with compliant hardware.

900MHz isn't internationaly recognized and 2.4GHz varies from country to country in terms of exact frequency range and power levels so the only truly universal RC band is 27MHz (and nobody with half a brain is going to be using that for giant scale :-)

The truth is that there are already a large number of RC bands around the world and here in NZ we can use almost all of them: (27, 29, 35, 36, 40, 72, 2.4GHz). The fact that most RC manufacturers have no problems supporting some or all of those bands would indicate that the viability implementing yet another band would be very high.

And there's no reason why the new band would have to be an international standard -- 72MHz certainly isn't -- you can only use it legally in a handful of countries outside N.America.

The real reason that 2.4GHz was chosen as the latest RC band by manufacturers is simply because there's a good range of cheap and readily available chipsets that can be pressed into service. Basically we have the manufacturers selling us gear on a "what's best for the manufacturer" rather than a "what's best for the customer" basis. It is interesting to note that the most technically sophisticated 2.4GHz RC system on the market (Futaba FASST) uses a chipset that isn't "off the shelf" but custom-designed and built by Futaba themselves -- which probably also explains the delay in getting some of their systems to market. I don't fly Futaba but (putting my "objective" hat on) I do feel their offering is trechnically superior to the others (GUID issues aside) and that's largely because they're not just trying to use components designed for some other purpose -- with all the attendant limitations that involves.

I can bet you any money you like that if the FCC allocated a chunk of dedicated spectrum to RC use the manufacturers would start rolling out gear for that band. It may be a little more expensive than the cheap 2.4GHz stuff that (except for Futaba) is built from repurposed off-the-shelf chipsets -- but when you're flying a model worth $x(x)K then this extra money becomes an investment, not a cost.

We now have the technology to implement a no-clash narrowband RC system that (on dedicated spectrum) will provide all the safety of an SS system but without the risks of sharing your swimming pool with sharks (so to speak).

[Panzlflyer]

I cannot understand why people keep wondering what will happen at Nall etc....people its already been done on a large scale and was in your AMA mag....300 or so on 2.4, the sky didnt fall in nor did helis crash left right and center, in fact there were none.
If you cut thru the over inflated figures put out over the pa at Nall there were not that many flying, the only real good crash I saw was on 72, so I guess you'all left on 72 need to be banned as youre not safe!!!

[dick hanson]

Sort of reminds one of the guys who predict a date for the world to end
then -when it does not happen as predicted -- a ongoing search is held to find why it didn't and find the next date it certainly will end.
There is a sh-t load of Spektrums in our area -some Futabas and some XPS
they all play nicely with each other and 99.9% of the time they all work as intended .

[Panzlflyer]

In fact my buddy on 2.4 said the only thing he noticed was that his Spektrum unit would not transmit sometimes as it couldnt find a channel clear.
Works as advertised.
I have noticed mine takes longer to link the more units are at the flightline so it is checking something?

[XJet]

	Quote: Originally Posted by dick hanson
	There is a sh-t load of Spektrums in our area -some Futabas and some XPS they all play nicely with each other and 99.9% of the time they all work as intended .

Yep, the sky isn't falling -- but there are some of us who'd rather not play football on a mine-field, even if there is just one mine somewhere out there in a maze of 1000 squares of turf.

That 0.1% figure (your stats :-) is the one that worries some people, and quite rightly.

The general observation with most 2.4GHz systems is they work really well -- until they don't.

I just think it would be a damned sight more sensible to rent a mine-free playing field (by way of leasing a tiny chunk of spectrum through the FCC) than to simply hope your next flight isn't "unlucky number 1000".

2.4GHz *is* a bit of a minefield and some of the technology being used to negotiate it is not as good as it could be. The whole reason for this thread (now) is to report the result of tests that enable folks to see what kind of protection their chosen (or yet to be chosen) system provides against losing a leg to a rogue mine of 2.4GHz interference.

When the 72MHz band was established, an RC model was a relatively low-performance, low-weight, low-energy vehicle that was not seen as representing any threat to public safety. My how things have changed.

Now we have giant scale birds with engines nudging 20HP, spinning carbon-fiber meat-slicers at 7K RPMs, and weighing in at over 50lbs. We also have turbine-powered birds with speeds of up to 200mph and an incredible amount of kinetic energy. These things are *lethal* and therefore I think the modelling community now has a very strong case for being granted exclusive use of a small chunk of spectrum.

And when you consider the risks involved if one of these new-generation models goes out of control, I think it's *really* important that people know the nature of the 2.4GHz environment they're flying in and the deficiencies (such as a lack of frequency agility in the case of XPS) of any RC gear they might be using (hence the creation of this thread in the first place).

Some folks will prefer not to know the facts -- that's their right, and if that's the case then this thread will be of no value to them so I expect they'll just unsubscribe.

[dick hanson]

	Quote: Originally Posted by Panzlflyer
	In fact my buddy on 2.4 said the only thing he noticed was that his Spektrum unit would not transmit sometimes as it couldnt find a channel clear. Works as advertised. I have noticed mine takes longer to link the more units are at the flightline so it is checking something?

Sounds right to me -
That is how it is advertised to work-and-as I have had a LOT of spare time indoors recently _I have played with reset times - using various rx --looking at boot up times -on and on.
Also tried to make my 9303 link up with both a 7000 and a 921 rx at the same time --best I got was one rx working and the other one just making the servo shudder -but not work
Apparantly they setup the 1024 and 2048 such that there is no way both will operate at the same time
Bottom line
either it works right - or it doesn't work at all- fine with me
I remember very well a NG 72.xxx rx that worked well on the bench and at the field - for about 100ft - problem was -The plane was airborne in about 50 ft.
So for me -my 2.4 Spektrum stuf is better than any system I previously owned.
It either turns on and goes or it does not - and that has happened a couple of times
but just like my computers -I reboot and all is fine
I can live with that.

[Pale Rider]

	Quote: Originally Posted by XJet
	Yep, the sky isn't falling -- but there are some of us who'd rather not play football on a mine-field, even if there is just one mine somewhere out there in a maze of 1000 squares of turf. That 0.1% figure (your stats :-) is the one that worries some people, and quite rightly.

And whats the percentage of possible failure/interference with 72 ? Its certainly not 100% either.

[Kiwi]

	Quote: Originally Posted by Pale Rider
	And whats the percentage of possible failure/interference with 72 ? Its certainly not 100% either.

No but 72Mhz is not sold as a system that will beat interference by hopping to a new channel where as XPS is supposed to. Spektrum is supposed to lock onto two clean channels and stay there. FASST is supposed to use every nook and cranny in the available specktrum to keep you hooked up.

2.4 is absolutely marketed as the answer to all the interference problems.

What we want to acertain now is:

Does it work as advertised

How does it handle a rotten environment

At the end of the day who has the most robust system if there is one. Maybe they all have strong points and weak points, but lets wait and see.

Apart from some of the IPD type receivers in 72Mhz, there is no real difference between brand A and brand Z. As a very talented man (responsable for the obtaining 72Mhz for RC use in fact) told me. FM, PCM, IPD, whatever, the only difference is the way you crash, but you do crash.

But with 2.4 Ghz its a totally new ball game. No one manufacturers system is equal to the other and they all claim to be the best.

Lets find out.