Independent tests prove lack of frequency hopping with XPS

[KrisW]

	Quote: Originally Posted by BZFrank
	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

first off, those German guys are very hard core modelers. . cold. . windy .. yuck

Second, that is one short, and narrow runway, for a turbine job

Third, the guy flying did a great job getting the plane down in one piece.

And lastly. . the radio system LOCKED OUT, several times. they were very lucky to get the plane back and be able to fly it another day.

[KrisW]

double post, sorry

[Prof. Dr. YoMan]

	Quote: Originally Posted by Kiwi
	FUTABA FASST absolutely does what they claim and you can see that on the scanner.

Except that they switch frequency every 8ms only, but not as advertised every 2ms.

They send out 2ms long Bursts every 8ms.

[BaldEagel]

	Quote: Originally Posted by aviti
	My point is who cares if it CAN hop. If it doesn't hop at the point it is needed then the plane is in the ground. I don't know if it needs to hop or not but with all the controversy surrounding this deal, I'd rather not find out with my plane.

I have to admit, I also don't care if it hops or not, what I don't want to be doing is flying an aircraft that keeps locking out on me, which is what happened to me on my interferance prone site, just like flying PPM with lock out instead of glitches.

Mike

[xed]

	Quote: Originally Posted by BaldEagel
	I have to admit, I also don't care if it hops or not, what I don't want to be doing is flying an aircraft that keeps locking out on me, which is what happened to me on my interferance prone site, just like flying PPM with lock out instead of glitches. Mike

Well if you do not care if it hops than you should also not care if your plane goes nose first into the ground either because that is what will happen when XPS encounters interference.

XPS is equivalent to an expensive PCM receiver running on one channel that may co-exist with other 2.4GHz systems until it can no longer cope with the level of noise on the startup channel it settled upon when you first turned on your XPS system. So yes, it will be fine to fly on it until another system trounces all over your channel.

Would I care if it was a foamy? Nope.

Would I care if it was a giant scale flying hunk of a plane with a metal missile strapped to the nose? Hell Yes!

Buyer beware...

[Four Stroker]

I ordered a really cheap Spektrum Analyzer here:

http://www.dunehaven.com/minisa.htm

Although not as fancy as the WiSpy, it has about the same performance. I will report if it works as advertised. If not, it was $96 total shipped.

[klhoard]

	Quote: Originally Posted by xed
	. . .<snip>. . Buyer beware...

.
.
I don't really care about the (informed) buyers, its the innocent bystanders that I'm worried about!!
.
.

[Flyfast1]

Even if the XPS system does not change channels in response to interference on the channel currently being used, it's at least as safe as conventional 72MHz systems. I think it's actually much safer than these systems since the transmitter is bound to a particular receiver, so that data from other systems on the same channel can be ignored. It also retransmits information several times without having to wait for the next frame. It also has failsafe functionality that many PPM systems do not have. But, from my own experience, the receiver is more sensitive to installation location and orientation than convention 72MHz receivers, so I think more time needs to be spent on installation and range testing. I am also assuming that an appropriate on-board electrical power supply system is used.

I also had to make a comment on that video. Wow, those guys are hardcore! And I thought my runway was narrow! That pilot did a great job of bringing that jet down.

-Ed B.

[JimC-MD]

	Quote: Originally Posted by 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.

Xjet,

This thread has been a chore to digest at times, but that has to be the post of the month

Sorry to hear about the training being on hold. I hope it gets worked out soon.

[Wojcigitty]

	Quote: Originally Posted by Flyfast1
	Even if the XPS system does not change channels in response to interference on the channel currently being used, it's at least as safe as conventional 72MHz systems. I think it's actually much safer than these systems since the transmitter is bound to a particular receiver, so that data from other systems on the same channel can be ignored. It also retransmits information several times without having to wait for the next frame. It also has failsafe functionality that many PPM systems do not have. But, from my own experience, the receiver is more sensitive to installation location and orientation than convention 72MHz receivers, so I think more time needs to be spent on installation and range testing. I am also assuming that an appropriate on-board electrical power supply system is used. I also had to make a comment on that video. Wow, those guys are hardcore! And I thought my runway was narrow! That pilot did a great job of bringing that jet down. -Ed B.

Yes, it is able to coexist on the same frequency as another 2.4 ghz device, and it is a lot "smarter" in how it's bound receiver-to-transmitter.

However, it's to be expected that, out of nowhere, another device could start broadcasting on the same frequency as XPS and use up all available bandwidth. FASST and Spektrum have methods of dealing with this.

It's NOT expected that all of a sudden another device could suddenly take a single frequency on 72 MHz without warning. 72MHz systems are not designed to be frequency-agile, and when properly used (frequency control is implemented), they do not need to be. 2.4GHz systems ARE supposed to be frequency-agile, and even when used properly, they DO need to be.

[Wojcigitty]

	Quote: Originally Posted by BZFrank
	(German Kangaroo sub-zero death-defying flight of death) Frank

Hard man fly turbine in ice and snow.

Hard man easily deal with lockout and land jetplane on cratered minefield runway.

XPS for hard man. Yeeeeeaaaah.

[aviti]

Looks to me like any landing with a turbine on that runway would be considered a crash so who cares if you have lockout. You crash no matter what.