Independent tests prove lack of frequency hopping with XPS

[XJet]

Well I'm hoping I'll have a chance to finish off my test gear this week -- since I won't be flying -- some idiot drove over my transmitter today and totally destroyed it :-(

They'll pay for it but it'll probably be $20 a week which means the wife will scoop it out of my wallet and use it on frivolous things like the electricity and phone bills :-(

[ricoalonso]

	Quote: Originally Posted by XJet
	Well I'm hoping I'll have a chance to finish off my test gear this week -- since I won't be flying -- some idiot drove over my transmitter today and totally destroyed it :-( They'll pay for it but it'll probably be $20 a week which means the wife will scoop it out of my wallet and use it on frivolous things like the electricity and phone bills :-(

Are you serious? Did you check if he is an XPS fan? Ok, that was a joke! But seriously, sorry to learn that. That's why I'm always hesitant to lay my Tx on the ground... so afraid someone might step on it.

^R^

[Flatlandman]

	Quote: Originally Posted by aviti
	Same assumption on your part that it is hopping.

I never said that it does hop but i will tell you that im pretty sure it will and does but i dont know when it hops or if it hops enough to make a difference. I hope we get some data that tells us when it does hop and i hope we can determine if its useful or not.

[BZFrank]

	Quote: Originally Posted by ricoalonso
	Edit: BTW, here the link http://www.rcgroups.com/forums/showt...816984&page=36 check post #535

Thanks. That 'video' proof looks a bit inconclusive to me - it only shows that XPS did not go into failsafe after some tries, not that control is maintained. This is consistent with some 'lockout' reports which report that while the link was down, the system did not get into failsafe. I suggest to repeat that test with a frequency analyzer running in parallel. Xjet - could you add this to your test cases if possible? Also it took how many tries to achieve this result?

I don't think that any hopping scheme that only works 'sometimes' to 'almost never' in the face of interference meets my personal criteria of a dependable RC control.

Frank

[DesertHucker]

	Quote: Originally Posted by XJet
	Well I'm hoping I'll have a chance to finish off my test gear this week -- since I won't be flying -- some idiot drove over my transmitter today and totally destroyed it :-( They'll pay for it but it'll probably be $20 a week which means the wife will scoop it out of my wallet and use it on frivolous things like the electricity and phone bills :-(

Sorry XJet don't have a TX to send you, hope it did not have the XPS module in it!

Bad luck hope you get it sorted and back in the air.

[XJet]

Strangely enough, it didn't have an XPS module in it at the time -- but come to think of it, I don't think that would have helped -- it wouldn't have hopped out of the way of the oncoming vehicle anyway:-)

It's not my only transmitter -- but I did have a few regularly-flown models programmed into it and it was half of the club's buddy-box setup so there won't be any training going on around here until it's replaced.

[klhoard]

	Quote: Originally Posted by XJet
	...<snip>. . -- it wouldn't have hopped out of the way of the oncoming vehicle anyway:-)...<snip>..

.
.
Now THAT's funny!!
.
.

[ss40]

Quote KrisW:We also have many cases of total loss of control of the aircraft, and the plane then crashing, instead of recovering control through the XPS unit regaining a data link. . again proving that on an all too frequent basis XPS somehow loses link, does not regain it, and the result is a lost aircraft EVERY TIME.

We do have the same comments regarding Spectrum setups here and there. I believe this is not really a fair statement. Just MHO of course.

[KrisW]

	Quote: Originally Posted by ss40
	We do have the same comments regarding Spectrum setups here and there. I believe this is not really a fair statement. Just MHO of course.

Ahem. . . the reasons for the Spektrum problems are documented. . usually battery voltages too low. Spektrum has addressed most of the issue, and also has a quick re-link firmware upgrade as well. Spektrum is also dual path, not single channel like XPS, making the likelihood of total signal loss almost impossible. I do not recall any incidents of Spektrum locking out, and I've searched back 6 months on all of the forums to see if any such total lockouts were reported on Spektrum with DSM2. Someone was trying to say one of the Park Flyer receivers losing link at long range was the same as one of the larger DSM2 modules losing link, but that's grapes versus watermelons, and an inaccuratte analogy.

Has anyone ever seen a Spektrum DSM2 go into failsafe that was NOT associated with low battery voltages? Has anyone ever seen an XPS go into lockout, not re-link, and crash the plane??

You will find the latter occurence to be well documented . . and the former to be literally nonexistent.

[ricoalonso]

	Quote: Originally Posted by ricoalonso
	... <snipped>... Edit: BTW, here the link http://www.rcgroups.com/forums/showt...816984&page=36 check post #535

Hey guys, I apologize for posting the link above here in FG. It turn out that it was a hoax or a bad joke from the original poster as he had admitted in RCG.

So sorry...

^R^

[Foamaholic]

That's okay, faked me out too. Mine didn't seem to fake anyone out.

[ricoalonso]

LOL! yeah, your video was at least very clear that it was all just for fun.

[Flyfast1]

	Quote: Originally Posted by KrisW
	Has anyone ever seen a Spektrum DSM2 go into failsafe that was NOT associated with low battery voltages? Has anyone ever seen an XPS go into lockout, not re-link, and crash the plane?? You will find the latter occurence to be well documented . . and the former to be literally nonexistent.

Chris,

How does the lockout mode of the XPS system work? Is this a mode where the receiver stops processing received data until some criteria are satisfied? I have been an XPS user for about 8 months and use the system in several quarter scale warbirds (100"+) and am always interested in learning more about the system. I have reviewed the documentation provided by XPS and the information on the XPS user group and cannot find anything that describes the lockout mode.

My system has been working quite well, but I am very careful about receiver installation and my electrical power system. I also conduct thorough range testing on the ground.

Thanks,

-Ed B.

[BZFrank]

	Quote: Originally Posted by Flyfast1
	Chris, How does the lockout mode of the XPS system work? .

A 'lockout' is a situtation when the RX does not respond to the TX anymore for a substantial time duration. There is no special mode for that in a XPS system (at least it would not make any sense to implement such), it is believed an error condition of the XPS due to various causes - low voltage, bad reception, channel swamping or triggered by other external events. 'Lockouts' in XPS are reported both be transitory when control could be regained after some seconds and permanent when control could not be regained until crash.

Here is a video example of a transistory XPS lockout (German narration, however its easy to tell when its happens: 'kein Empfang' means 'No reception', 'Empfang' means 'reception', its was not a low voltage issue as a logger was running during flight):

YouTube - rc jet Kangaroo 2007-12-23 XPS LockOut ?

Frank

[XJet]

Just as a matter of interest, here are some quotes from posts JD has made to various forms in respect to XPS. I don't think I have to add anything:

"MaxStream has patents pending for the spherical technology (I would love to say I invented it, but that is not the case)"

"As part of the normal operation, the frequency changes on the fly (hopping) using a patent-pending technique"

"Everything stated on our website for the product description is 100% true. It may not be worded the way you like it, but that is marketing"

"Being prepared for the possibility of an issue when fully enclosing the antenna, both the transmitter modules and receiver are designed to accept remotely mounted "rubber ducky" (stubby) antennas"

"Their [the AMA] biggest concern is the affects of metal and carbon fiber. Considering that we can fully incase the receiver in either carbon fiber or steel, and it still works, we are not concerned about these affects"

"I won't explain the technology, that is what we consider trade secrets - and magic"

"I can tell you that just watching a specktrum [sic] analyzer with our system running and other 2.4GHz devices going, definitely shows that we have a much superior system for preventing any type of potential problem"

"If you flew your plane over a school with a huge 14dbi external 802.xx antenna, that would likely be cause for switching to a new frequency (away from whatever channel that 802.xx was on)"

"Even 2.4GHz cameras are not a problem as we can move around their frequency, even with huge drift that occurs in the cheap overseas versions"

"now if anyone had bi-directional communication, telemetry support, and about 1/2 the price that would be impressive! ... oh wait, that's us! "