Independent tests prove lack of frequency hopping with XPS

[KrisW]

	Quote: Originally Posted by XJet
	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 :-)

Actually, I thought something that was related to more than one country at the same time was considered "International" or at least trans-national. . thus the title that 900 mhz is an international frequency. And yes, most countries have their own little way of doing things on 2.4 ghz. . just the nature of independent nations doing what is best for themselves.

There are a lot of people holding 2.4ghz up as the panacea for all problems RF related in our hobby. Sorry, but every thing that has been thrown out so far, in the way of things that are supposed to hop frequencies, dodge other transmissions, and keep you linked to your receiver . .well . .all of them CAN go wrong, and have proven it more times than necessary to prompt a very loud Caveat Emptor for those wiching to go 2.4g. Modeller beware .. things are not as perfect as the slick advertising, slogans, and technical data overload would have you believe.

When someone invents a system that NEVER has a problem caused by outside sources, then I'll be a lot more interested. That has not happened yet, and the opposite seems to be the rule. . every system has a problem of some sort, be it quirky frequency changing, a limited number of channels it has access too, UID glitches, or just plain old "someone walked all over me with a huge signal". It happens. Still.

This is a great discussion. . I hope it continues.

[zoomer260]

	Quote: Originally Posted by XJet
	I can't believe that the AMA hasn't approached the FCC for a small slice of dedicated spectrum that can be allocated solely for model RC use. Sure, this might cost money - but amortize it across all the model-fliers and you'd find that it was a pretty small price to pay for security against having your 40% gaser shot down by some kid with a park-flier or some quite legal burst of sustained noise on 2.4GHz. Given that only a handful of models can fly at the same field at the same time, only a very small chunk of spectrum would be needed for a narrow-band system (like we've been using for decades) and the shoot-down problem could easily be handled by smart transmitters that automatically negotiate an available frequency at power-up (even the Polk Seeker synth transmitter listens before it will transmit and refuses to emit RF if the chosen channel is in-use). How about the AMA approaches the FCC to see what bureaucracy and costs are involved in grabbing a single MHz or even 500KHz of bandwidth somewhere? Remember that all this fancy SS technology on 2.4GHz is really only there to try and solve the frequency clash and interference issues that would effectively disappear with such a auto-negotiationg system on a dedicated chunk of spectrum. Thoughts?

I wonder if maybe somewhere along the line they did, seems reasonable, and got laghed out of the office !! "What ? For TOY PLANES ? HA !!

[zoomer260]

	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. 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.

I hate to be negative or the peanut gallery but if they (FCC) and govt. in general ever takes our toy planes as seriously as you suggest they will just BAN them. That's the way it works in this country. WE don't have and will never have the power to successfully lobby Washington.

[dick hanson]

	Quote: Originally Posted by Kiwi
	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.

The thing is -we all tend to read into the advertising what WE think -
Does it work as advertised ?
(free from interferrence)
As far as I can tell - a true statement -but if you read in - "does it stop working when signal is blocked or power drops below working level - -then the inferrence changes ".
How does it handle a rotten enviroment?
Again subjective - If you mean sloppy rattling pipe connections -it is better - if you mean an all carbon airframe - not as well as a 36"long antenna outside the carbon-
All in all my own preference is overwhelmingly the 2.4 Spektrum and here is why :
first - It has Model Match available - a real ,usable safety feature
secondly -there has been a ongoing improvment in size/type rx available for everything from 4 ounce models to 50 pounders . (I have had almost zero problems with any of my setups ) -
The XPS and Futaba FASST I have seen and flown also work just as advertised
So which is best?
maybe what suits your own needs best might be closer to what we need to know.
Some guys will give reasons why they are waiting or will not switch -
Obviously - they have their own feelings as to why.
OK by me.

-

[Leseirf]

	Quote: Originally Posted by zoomer260
	I hate to be negative or the peanut gallery but if they (FCC) and govt. in general ever takes our toy planes as seriously as you suggest they will just BAN them. That's the way it works in this country. WE don't have and will never have the power to successfully lobby Washington.

I had that very same thought when reading Xjets post on the lethality of our toys. Bringing that concept to the forefront could have us all back to flying Pico-Cubs in the back yard!

[zoomer260]

On a positive note, I am extremely grateful to all taking this thread serious enough to actually check it out,(that have the resources) see where each available system has it's each individual weakness for guys like me with little budget to to make an informed decision. I have since added Spektrum to JR as a choice. I love the JR Tx box feel and ease of JR programming. Keep it up !!

[KrisW]

	Quote: Originally Posted by Leseirf
	I had that very same thought when reading Xjets post on the lethality of our toys. Bringing that concept to the forefront could have us all back to flying Pico-Cubs in the back yard!

The technology has been known for a very long time . .that no one has used it for nefarious means is a blessing in disguise. Our radios are so abundant, it would take a gestapo crackdown to confiscate them, and even then they could still come across the border illegally from any number of countries. And, come to think of it. . 2.4 would probably be the first choice for most. . . . . . .of THEM.

It's NOT gonna happen, sorry.

[Kiwi]

One of the darker sides of 2.4Ghz is who else use it and who else does not like it.

God help it never happens and I actually have had this stuffed away and really felt I should never post this, but I see this as a mature discussion now and a lot of the opinions are giving way to one of the better threads we have running on the site.

Anyway imagine if litlle Johnny turns up close to the field with this puppy in his Tit pocket.

[DesertHucker]

	Quote: Originally Posted by Kiwi
	One of the darker sides of 2.4Ghz is who else use it and who else does not like it. God help it never happens and I actually have had this stuffed away and really felt I should never post this, but I see this as a mature discussion now and a lot of the opinions are giving way to one of the better threads we have running on the site. Anyway imagine if litlle Johnny turns up close to the field with this puppy in his Tit pocket.

Well KIWI what is it?

2.4g jammer!

[Kiwi]

That thing will blow every 2.4 Ghz device off the map within 150 feet of it being activated. Problem is the ar$ehole who advertises these things offers to make em stronger if you need MORE POWER!!!!!!!

I suppose I'm a bit paranoid when it comes to what can be done with 2.4. With 72Mhz you never ever seen a device like this advertised on Ebay. But with 2.4 you do.

That particular one does 800, 900 and 2.3 Ghz. But you get them in what ever flavor you want mail order.

[erichevy]

What is the apparatus Kiwi? What does it do, and where is it for?
Be more specific please!

Eric.

[xed]

	Quote: Originally Posted by Kiwi
	I suppose I'm a bit paranoid when it comes to what can be done with 2.4. With 72Mhz you never ever seen a device like this advertised on Ebay. But with 2.4 you do.

Well in theory, if you a real *!(@$(^, you can buy a $50.00 Hobbico frequency scanner with an external antenna from pretty much any hobby store and sit behind a bush with a 72MHz synthesizer capable transmitter and pick off planes and helis at will...